Path to Villainy

[Miseo]

Brutal. I like it.
I can see that being the absolute final step. The ultimate betrayal. But it only works as the final step, the "straw that broke the camel's back." Personally, if I were writing this (and the only way I can give advice is if I, at least temporarily, imagine myself writing it), I would show every step of the journey. Show every time he had to betray an ideal "for the greater good." Show every situation where those he relied on failed him. Show every torturous step.

Yep. That is the straw that broke the camel's back. As you suspected, he is immortal (so are the 12 antagonists (as you can imagine it is a very long battle)). He is an undead, and of a vampiric subtype (although still a bit different from vampires). He was killed by a dark god named Iah who bit out his throat. The image of Iah biting him to death was overlaid into himself (a type of magic called impartation) so he gained a portion of Iah's power and also the need to consume others. He begins his journey with the intention of finding out what happened to him and also to find answers for the unfortunate demise of someone he cared about (the events of volume 1). He gets dragged into a war between the Church and the Circle (a group of evil gods). And over time the quest to stop the Circle becomes more and more imperative, and the costs of doing so increase more and more.

I suppose then that the best course of action is to make the costs and consequences of doing so darker and darker?

 

[Christopher Michael]

You prove my point. If someone's paradigm of good and evil shifts, even to polar opposites as such with these individuals you will find that they would say that they were the heroes of their own stories.

Which is the precise opposite of what I understood your point to be. Because by shifting to the polar opposite, they have, in fact, abandoned what they saw as good. They may have replaced it with something else, but the abandonment has occurred.

Read 'Paradise Lost' by John Milton, and then tell me whether the devil is the one with the horns or the halo.

I have. Several times. Although I find Satan in there to be compelling, even complicated, I find him to be the most despicable creature to ever walk the pages of literature- something I believe to have been Milton's entire aim.

 

[Christopher Michael]

I suppose then that the best course of action is to make the costs and consequences of doing so darker and darker?

Exactly. Increase the risk. Increase the cost. Increase the consequences. And never go back to the same well twice. (If he does A and it leads to B...I would never have him do A or cause B again- certainly not in conjunction with each other.)

 

[Alyssa]

Michael makes some good points. Another thing to consider is that your MC has been chosen out of all of humanity to represent Bel as his mortal avatar. That seems like something that would really mess with someone's head and could internally sanction all sorts of things that someone normally wouldn't do. Your MC could very well end up viewing themselves as the best of humanity and end up justifying it with the fact that he was chosen by a primarily good god.

 

[Demesnedenoir]

I was going to answer betrayal as the driver that can totally shift a persons POV, seems you got that going on.

I've got a side character who becomes "tainted" by a consciousness of "evil" and while he starts as just an average Joe nice guy, evil begins to use the tiny flaws in the guy's character... primarily jealousy and pride... to convince him that those in power are not giving him his due, betraying him and all his people. I'm hoping to take this on a very subtle arc through book 2 & 3, so nobody really knows the catalyst of evil, I want the reader to even question if he isn't right about the whole damned conspiracy to screw him and his people over.

Yours sounds less subtle, but humans have a near infinite ability to rationalize their actions, you can see it in the modern world where rioters will set cars on fire... who's car? Doesn't matter, just some poor schmuck who picked the wrong parking spot. And that's a minor justification compared to so many truly evil things.

 

[Peat]

As the months turn into years and centuries, he gets pulled more and more into events against his will and always ends up losing the people he's supposed to protect. So his humanity becomes sullied by bitterness.

Be careful here. It sounds like your character might be being reactive instead of proactive - constantly being made to stuff rather than choosing to do stuff - and that's classically a good way to lose readers. While situations will undoubtedly play their part in turning the guy into a villain, for him to be an interesting PoV character you need to make clear that ultimately, its *his* choice.

I've just thought of a (possibly slightly weird) way to view this. People become villains by betrayal, right? Either they betray the side they're on or they betray their own ideals. Here's a list of reasons why people become traitors that I've just cribbed from a game - its a pretty good one I think.

1) You think the world/your friends don't recognise your talent and you can get that recognition by betrayal

2) You need something and can get it easiest/can only get it be betrayal

3) You want money/something else and don't mind betraying people to get it

4) You are missing something normal in your life (i.e. food, love) and can get it through betrayal

5) You hate people who you can only destroy through betrayal

6) You think the world and yourself should burn and betrayal offers the best chance to do so

7) You think the world will be a better place and its genuinely the right thing to do to betray



Its not a perfect list but I do think it provides most of the solid motivations for that sort of volte face, particularly when you start mixing them together. I mean, take the Forsaken from The Wheel of Time. Ishmael is a mix of 6 and 7 - a nihilist who believes that its better to accept its all over. Asmodean is a mix of 1 and 5 - he wants the world to recognise he's the man and poop on those who think they're better than him. Actually, a lot of them are 1 and 5. Lanfear is 3 and 5, with the thing she wants being some sweet Dragon lovin'.

So from what you're saying with the betrayal, that would probably be a 5, with maybe a 7 if he's come to the opinion that the people who betrayed him are actually the evil ones.

 

[Miseo]

Michael makes some good points. Another thing to consider is that your MC has been chosen out of all of humanity to represent Bel as his mortal avatar. That seems like something that would really mess with someone's head and could internally sanction all sorts of things that someone normally wouldn't do. Your MC could very well end up viewing themselves as the best of humanity and end up justifying it with the fact that he was chosen by a primarily good god.

That's a good idea. And it opens another door to more internal struggle... because after he gives up his humanity for power and becomes a monster, although he still bears the mark of Bel, one of the main antagonists for the next section of the story is another person who bears the mark of Bel (although I say antagonist, he's actually a good guy). When you think about it... that could really screw with his mind. Jealousy, and even the feeling of being abandoned by Bel, who gave him the mark all on his own. This could go places.

I was going to answer betrayal as the driver that can totally shift a persons POV, seems you got that going on.

I've got a side character who becomes "tainted" by a consciousness of "evil" and while he starts as just an average Joe nice guy, evil begins to use the tiny flaws in the guy's character... primarily jealousy and pride... to convince him that those in power are not giving him his due, betraying him and all his people. I'm hoping to take this on a very subtle arc through book 2 & 3, so nobody really knows the catalyst of evil, I want the reader to even question if he isn't right about the whole damned conspiracy to screw him and his people over.

Yours sounds less subtle, but humans have a near infinite ability to rationalize their actions, you can see it in the modern world where rioters will set cars on fire... who's car? Doesn't matter, just some poor schmuck who picked the wrong parking spot. And that's a minor justification compared to so many truly evil things.

You make a fair point. Humans are very exceptional at excusing their own actions while vilifying those of others. I could definitely use that perspective in my own story.

 

[Miseo]

Be careful here. It sounds like your character might be being reactive instead of proactive - constantly being made to stuff rather than choosing to do stuff - and that's classically a good way to lose readers. While situations will undoubtedly play their part in turning the guy into a villain, for him to be an interesting PoV character you need to make clear that ultimately, its *his* choice.

I've just thought of a (possibly slightly weird) way to view this. People become villains by betrayal, right? Either they betray the side they're on or they betray their own ideals. Here's a list of reasons why people become traitors that I've just cribbed from a game - its a pretty good one I think.

1) You think the world/your friends don't recognise your talent and you can get that recognition by betrayal

2) You need something and can get it easiest/can only get it be betrayal

3) You want money/something else and don't mind betraying people to get it

4) You are missing something normal in your life (i.e. food, love) and can get it through betrayal

5) You hate people who you can only destroy through betrayal

6) You think the world and yourself should burn and betrayal offers the best chance to do so

7) You think the world will be a better place and its genuinely the right thing to do to betray



Its not a perfect list but I do think it provides most of the solid motivations for that sort of volte face, particularly when you start mixing them together. I mean, take the Forsaken from The Wheel of Time. Ishmael is a mix of 6 and 7 - a nihilist who believes that its better to accept its all over. Asmodean is a mix of 1 and 5 - he wants the world to recognise he's the man and poop on those who think they're better than him. Actually, a lot of them are 1 and 5. Lanfear is 3 and 5, with the thing she wants being some sweet Dragon lovin'.

So from what you're saying with the betrayal, that would probably be a 5, with maybe a 7 if he's come to the opinion that the people who betrayed him are actually the evil ones.

First, I shoud point out concerning the proactive vs reactive thing... it's a bit of both. It's all his choice yes, but at the same time it isn't. The one who set him on his path, Iah, is a dark god who presides over time. And he has lived through history many times, trying to find a way to make his desires become a reality. And he found it. Iah literally pretty much planned out Sorin's entire life before he was even born. He even created entire cities just to stage future events to nudge Sorin in the direction he wants. So while it seems like Sorin is doing things on his own the fact is he's being drawn into everything by Iah's manipulation of events. It's a bit of a mess, but it's terribly fun to plan out.

And while 5 seems like a viable explanation, personally I would say that it's more a mixture of 2 and 6. While he turns on the world and tries to subjegate it as vengeance, his psyche is a lot more twisted than this. He doesn't want to destroy the world and the people he fought to protect. He wants them back... and in his mind, the best way to do that is by destroying them and forcing the world to bend to his will. In a sense, he's trying to save what's precious to him by destroying it.

 

[Alyssa]

Why not make Sorin aware of Iah's influence? Make him act out and make deliberately irrational decisions as a way of trying to ruin Iahs plans. Leading to even greater misery and heartache


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[Miseo]

Why not make Sorin aware of Iah's influence? Make him act out and make deliberately irrational decisions as a way of trying to ruin Iahs plans. Leading to even greater misery and heartache


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Possibly... but not until several volumes in. He does not even come to know the actual identites of his enemies until the end of volume 3, where he meets them in person when the kingdom of Valdis falls (which was, of course, his own fault, because Iah is a magnificent bastard). Until then he only knows Iah as "the man in white", and is aware that a man named Phrike was responsible for the destruction of Acre and that Iah might have been involved.

 

[Alyssa]

Trying to ruin your character's life is fun


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[Miseo]

Trying to ruin your character's life is fun


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Oh. Hell. Yes.

This is a character where nothing goes good for him. Even while he's still good, he feels responsible for the cataclysm that followed from the fall of Valdis which changed the world and killed countless people.

Sometimes I think I torture him too much...

 

[DragonOfTheAerie]

Gaaaaahh! I'm so mad. I came to this conversation late. AND ITS ABOUT MY FAVORITE THING!

(Tormenting and taunting and twisting people into monstrous perversions of their forever selves? Yes. My favorite thing. )

First of all, I'd like to say that often, what makes a hero a hero and a villain a villain is relative. It depends on the lens. How many Bad Things does a hero have to do to stop being a hero? How many Bad Things to become a villain? There isn't a number. So, a villain might not realize that the acts he commits are evil. A hero might not realize that the acts he commits are...as bad or worse than the villains! Villains and heroes are fundamentally the same; they want something, they're trying to get it. Theoretically they're on different ends of the moral spectrum, and that's what divides them. But the divide is murky. The only real difference is from what angle we're viewing the story.

I don't think anyone thinks of themselves as "mwa-ha-ha-ha-haa! EVUL!" Many villains believe themselves to be in the right. From their POV, they ARE the hero. For some their goal is more important than morality (or they use the end to justify the means.) Some others just don't give a damn about morality. They want to achieve their goal and whoever wants to get in the way, well, sucks to be you! Some are made to believe themselves to be monsters, and come to embrace that identity. Some are just so damaged and twisted by their lives and circumstances that they can't function like a normal person and feel empathy, etc. There are a few that just want to cause as much suffering and damage as they can for no apparent reason and laugh maniacally while doing it. (But I don't think that last kind are very common. Or interesting.)

But! A lot of that is beside the point. How do you drive a character who starts out as basically good to evil?

I think the seed of evil has to be there in the beginning. Something in this character has to have the potential to develop into something dark and dangerous. Maybe it's a deep-rooted bitterness, or a lust for power, or any desire so keen they will use any means to achieve it. Making a person go through awful things doesn't make them evil. Lots of people go through awful things and don't become evil. There has to be something there in the beginning that offers the potential, however slight, to become more important than any other conviction and override morality. Or, something that already contradicts the character's moral values and could, if the character let it, win. Something at the beginning, anything. Something that, with the right push, could take this character over. I dont know...but don't think all characters have the potential to become evil. Some are just very deeply good, and nothing is strong enough to sully that. (Unless, perhaps, they are deeply, deeply blinded by a conviction they have, more powerful than other values and convictions? A conviction that is good essentially in the end, but the means are evil? Idk. I'm considering this.) So it's good to take a look at what's inside your character at the start. What could, if twisted or strengthened or brought fully into the light, could become the beginning of evil? Could motivate it? Could clash with the good in your character, and in the right circumstances, win?

In a situation like this, there will be conflict between darkness and light. The darkness must become stronger to win. What will strengthen that darkness, whatever form it takes? What will weaken that light?

Your character already is struggling with his dark, monstrous nature. So you do have something at the beginning. But his convictions or good nature are strong enough to win out at first. What gives that push that changes everything? Hmmm...

Here comes the fun part.

Often the extra push comes in the form of awful things happening to your character that augment their fear/anger/hatred/bitterness/pain and kill the love and happiness inside them. When bad things happen to some characters, their nature or convictions prevents their pain from getting the better of them. But some characters react to horrible events happening in their lives differently. Maybe they react with hatred and anger against what hurt them. Maybe they are simply hurt too much, and without any light in their life to give them comfort and meaning, that becoming heartless and fiercely pursuing whatever goal they have is the only way to find comfort and meaning. The saying is true: hurt people hurt people.

So take away people your villain-to-be loves. But I don't think this is entirely about just causing them pain. It also starves them emotionally, leaves them with needs unmet. Perhaps it robs them of a mitigating factor on their darker nature--we often have people in our lives that help bring out the best in us, and if your character has such a person in their life...ripping them away might hasten their descent into darkness.

People with unmet emotional needs have to fill the void somehow. Filling the void might be a desperate enough desire to drive evil acts. So take from them things they love, the things that bring them happiness, the things that give them meaning. Don't just make them hurt. All of your characters will hurt. Make their whole life broken and incomplete. So much so, that they must give in to their worse nature, in a vain attempt to patch themselves together.

The even more fun part: You can have your character see themselves becoming something monstrous. And they fight that nature. They try to believe that they aren't. But, if they see themselves starting to give in, or slipping accidentally into the darkness inside...they might start to believe that they are evil on the inside. They might start to believe the darkness has won. And that might be the final push. Because if you're a monster, or believe yourself to be, do you agonize in it, or do you accept that about yourself? Acceptance might be easier.

I think there's always a choice involved in slipping into evil. But to drive your character to evil, you have to make the choice to become evil the easy option. Otherwise is too hard, too painful. Otherwise deprives your character of what he most wants. And he can't handle that.

 

[Miseo]

Gaaaaahh! I'm so mad. I came to this conversation late. AND ITS ABOUT MY FAVORITE THING!

(Tormenting and taunting and twisting people into monstrous perversions of their forever selves? Yes. My favorite thing. )

First of all, I'd like to say that often, what makes a hero a hero and a villain a villain is relative. It depends on the lens. How many Bad Things does a hero have to do to stop being a hero? How many Bad Things to become a villain? There isn't a number. So, a villain might not realize that the acts he commits are evil. A hero might not realize that the acts he commits are...as bad or worse than the villains! Villains and heroes are fundamentally the same; they want something, they're trying to get it. Theoretically they're on different ends of the moral spectrum, and that's what divides them. But the divide is murky. The only real difference is from what angle we're viewing the story.

I don't think anyone thinks of themselves as "mwa-ha-ha-ha-haa! EVUL!" Many villains believe themselves to be in the right. From their POV, they ARE the hero. For some their goal is more important than morality (or they use the end to justify the means.) Some others just don't give a damn about morality. They want to achieve their goal and whoever wants to get in the way, well, sucks to be you! Some are made to believe themselves to be monsters, and come to embrace that identity. Some are just so damaged and twisted by their lives and circumstances that they can't function like a normal person and feel empathy, etc. There are a few that just want to cause as much suffering and damage as they can for no apparent reason and laugh maniacally while doing it. (But I don't think that last kind are very common. Or interesting.)

But! A lot of that is beside the point. How do you drive a character who starts out as basically good to evil?

I think the seed of evil has to be there in the beginning. Something in this character has to have the potential to develop into something dark and dangerous. Maybe it's a deep-rooted bitterness, or a lust for power, or any desire so keen they will use any means to achieve it. Making a person go through awful things doesn't make them evil. Lots of people go through awful things and don't become evil. There has to be something there in the beginning that offers the potential, however slight, to become more important than any other conviction and override morality. Or, something that already contradicts the character's moral values and could, if the character let it, win. Something at the beginning, anything. Something that, with the right push, could take this character over. I dont know...but don't think all characters have the potential to become evil. Some are just very deeply good, and nothing is strong enough to sully that. (Unless, perhaps, they are deeply, deeply blinded by a conviction they have, more powerful than other values and convictions? A conviction that is good essentially in the end, but the means are evil? Idk. I'm considering this.) So it's good to take a look at what's inside your character at the start. What could, if twisted or strengthened or brought fully into the light, could become the beginning of evil? Could motivate it? Could clash with the good in your character, and in the right circumstances, win?

In a situation like this, there will be conflict between darkness and light. The darkness must become stronger to win. What will strengthen that darkness, whatever form it takes? What will weaken that light?

Your character already is struggling with his dark, monstrous nature. So you do have something at the beginning. But his convictions or good nature are strong enough to win out at first. What gives that push that changes everything? Hmmm...

Here comes the fun part.

Often the extra push comes in the form of awful things happening to your character that augment their fear/anger/hatred/bitterness/pain and kill the love and happiness inside them. When bad things happen to some characters, their nature or convictions prevents their pain from getting the better of them. But some characters react to horrible events happening in their lives differently. Maybe they react with hatred and anger against what hurt them. Maybe they are simply hurt too much, and without any light in their life to give them comfort and meaning, that becoming heartless and fiercely pursuing whatever goal they have is the only way to find comfort and meaning. The saying is true: hurt people hurt people.

So take away people your villain-to-be loves. But I don't think this is entirely about just causing them pain. It also starves them emotionally, leaves them with needs unmet. Perhaps it robs them of a mitigating factor on their darker nature--we often have people in our lives that help bring out the best in us, and if your character has such a person in their life...ripping them away might hasten their descent into darkness.

People with unmet emotional needs have to fill the void somehow. Filling the void might be a desperate enough desire to drive evil acts. So take from them things they love, the things that bring them happiness, the things that give them meaning. Don't just make them hurt. All of your characters will hurt. Make their whole life broken and incomplete. So much so, that they must give in to their worse nature, in a vain attempt to patch themselves together.

The even more fun part: You can have your character see themselves becoming something monstrous. And they fight that nature. They try to believe that they aren't. But, if they see themselves starting to give in, or slipping accidentally into the darkness inside...they might start to believe that they are evil on the inside. They might start to believe the darkness has won. And that might be the final push. Because if you're a monster, or believe yourself to be, do you agonize in it, or do you accept that about yourself? Acceptance might be easier.

I think there's always a choice involved in slipping into evil. But to drive your character to evil, you have to make the choice to become evil the easy option. Otherwise is too hard, too painful. Otherwise deprives your character of what he most wants. And he can't handle that.

I have screenshot this response and put it in my storyist app. You made a lot of very good points, especially about the initial seed. As for the initial seed, while its true that he has a monstrous nature, for the most part the holy mark is enough to hold it back under usual situations. But there is something else there, hidden deep in his person. And that is fear. Volume 1 deals primarily with this, actually. Watching his family and friends killed in front of him traumatizes him, and he lives in fear and hiding for a long time. Afraid that if he lived in a place with others, the same hell from before would return. A young girl he meets helps pull him out of his fear, little by little, until she disappears. He tries desparately to save her, but an emissary of Phrike turned her into a monster (along with other missing children as an experiment) and he has to kill her to save her. Not to mention, the entire city they lived in is dragged into a special kind of hell and destroyed, so all the fears he had started to heal from become deeply ingrained.

His monstrous second nature could be the seed, but fear would be the soil it grows in.

 

[DragonOfTheAerie]

I have screenshot this response and put it in my storyist app. You made a lot of very good points, especially about the initial seed. As for the initial seed, while its true that he has a monstrous nature, for the most part the holy mark is enough to hold it back under usual situations. But there is something else there, hidden deep in his person. And that is fear. Volume 1 deals primarily with this, actually. Watching his family and friends killed in front of him traumatizes him, and he lives in fear and hiding for a long time. Afraid that if he lived in a place with others, the same hell from before would return. A young girl he meets helps pull him out of his fear, little by little, until she disappears. He tries desparately to save her, but an emissary of Phrike turned her into a monster (along with other missing children as an experiment) and he has to kill her to save her. Not to mention, the entire city they lived in is dragged into a special kind of hell and destroyed, so all the fears he had started to heal from become deeply ingrained.

His monstrous second nature could be the seed, but fear would be the soil it grows in.

I got screenshotted? Whoa, I'm honored.

And it looks like you're starting to figure things out. You really do put this character through hell, don't ya? I hate to make my characters suffer, but it's also kinda fun...

 

[Miseo]

I got screenshotted? Whoa, I'm honored.

And it looks like you're starting to figure things out. You really do put this character through hell, don't ya? I hate to make my characters suffer, but it's also kinda fun...

He's mah punchin' bag.

 

[Penpilot]

There aren't many. If I had to choose one, he will always try to protect those he is close to. This is because, before he became a total monster, he had tried to protect the people he loved, but to no avail. He was never able to protect the people important to him, and sometimes was indirectly responsible for what happened to them. But I wouldn't call this a moral belief so much as unresolved issues... more like an obligation, to make up for failing to protect the people he loved.

And of course even this he compromises on, even after he decides to redeem himself. Does a real dick move later in the story...

One way to take a character down the path of darkness is to give them a reason to compromise their values. You say he will always protect those he loves. What happens if two people he loves are about to die, and they can only save one? What if they have to choose between the life of someone they love and an innocent child? What if someone they love becomes twisted and they begin doing deplorable things? What will your character do about that?

Now the choices you character makes in situations like this will affect them and will drive them to see the world in certain ways. I believe in the view that everyone is the hero of their own story, and that very few people truly think of themselves as the villain. They may do villainous things, but there's always a 'good' reason for it.

I mean let's take a step back from fiction. In real life, most of us would agree that killing is wrong. But for many, there are circumstances where they would kill someone in a heartbeat. They wouldn't relish it. They'd feel bad about it, but given the same circumstance they would make the same choice again. Does that make someone a villain? In my eyes, no. But it certainly can lead one down a slippery slope of choices, where the range of circumstances becomes broader and broader in which one would feel justified in reacting violently.

And to me, things like this that can lead people to become what others consider villains.

 

[spectre]

Yep. I'm doing one of those protagonist journey to villainy stories. Sort of. Starts like this, protagonist is innocent, his journey brings him to the side of villainy, major plot point occurs and he tries to rectify his mistakes and redeem himself although he never quite stops being a villain.

So I'm wondering... anyone have any tips on developing a protagonist's character into that of a villain protagonist?

If it would help, I'll give some info on my character. He was chosen by Bel (God) to become a Saint (mortal incarnation of Bel). And has a mark on his body as proof. But before he can fully grow into a Saint he is killed by a powerful dark being and brought back to life as an undead creature. Normally such a curse would corrupt a person's soul and spirit entirely turning them into total demons, but because of the mark most of his humanity is left in tact. So there is the internal struggle of his innocent human nature and his darker, monstrous nature that desires to kill and feed.

As the months turn into years and centuries, he gets pulled more and more into events against his will and always ends up losing the people he's supposed to protect. So his humanity becomes sullied by bitterness.

But it needs more than this. People don't have to turn bad because bad things happen to them. And I don't want to rely on the whole "there's an evil curse on him making him evil" thing (although there is evil in him) because that's just lazy. It needs an extra kick. Loss of loved ones doesn't turn one evil. Loss of meaning doesn't turn one evil. These turn people bitter. And bitterness dulls people, immobilizes them.

What pushes a character to abandon all that is good?

I think among ALL the reasons mentioned which are palatable there had to be found some reward for changing sides. Power, revenge, abstaining from a former responsibility; etc. Darth Vader wanted power, Spawn revenge although he was more of an anti hero than a villain. Maybe your protagonist is trying to fast track his goals that remain in line with Bel, but are seemingly more nefarious making him look like a villain. The possibilities are endless.

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[TheCrystallineEntity]

I would like to make a story all about a hero doing hero-y things throughout the whole story, but then when he/she settles down in a castle or whatnot, the 'real' hero shows up to defeat the 'villain'.

 

[Christopher Michael]

One thing I didn't mention earlier, which I love doing, is taking your MC slowly but steadily down the slippery slope.
This is actually a thing that happens in real life as well. A series of decisions, individually seemingly inconsequential, forcing them to slowly but consistently sacrifice their morality one little slice at a time. One day they wake up and are the polar opposite of what they once were, where they thought they would be. And they have absolutely no idea how they got there, and no clue if they can return.
You have a Hero (yes, with the capital H.) A real Captain America type- from back in the Golden Age when he was incorruptible, and stood for everything that was good and right Because It Was The Right Thing. At least on the outside.
He faces a decision. Not something Life or Death. Something where both options seem right. One decision is absolutely the morally and ethically right thing, but the other one, while maybe slightly less Right, doesn't appear to be much (if any) worse. So he makes the Slightly Less Right choice. *Snip* There goes a little piece of his code.
Then another decision comes. Again. It doesn't seem like there's a major difference. So he takes the one that appears to him (her?) to be slightly less right. And another *snip*.
And another.
And another.
Soon he faces a decision that is much more important. Let's say a choice between saving someone (who is at risk of dying through only their fault) or walking away. He may wrestle with himself over it, but he's eroded his moral code. He walks away.
After a series of these decisions, not all of which have to be detailed, he's now in a place where making the wrong choice is simple. Where doing the wrong thing is not even a question. He's now the villain of your story, and it happened so gradually that he can't even realize it.