Repercussions and side effects for a truth telling superpower?

A great lack of trust in all of humanity.

an over-reliance on his abilty. Suppose one could thwart him. Would he know?

a lack of intimacy

a lack of people who trust him

sometimes lies are better so perhaps to much revealing of things better left unsaid.

 

can it be controlled or does anyone he touch automatically have to say the truth?

 

As others have said, do you mean the absolute truth, or the truth as the characters being touched understand it? Because those aren't the same thing. That might mean that the answers your main character gets aren't accurate - so how do they know when they've got an inaccurate answer? What consequences do those answers have?

Then there's the question of who else is around when your MC asks the questions. What happens if the person being asked hasn't told those around them what they think is the truth?

 

I once read a book with a character that had a similar power, the person being questioned was compelled to answer truthfully but felt horribly violated by it. As a consequence the character refused to use his power on anyone he cared about because it would violate their trust and possibly change how they felt about him. This actually led to misunderstanding that could have been easily avoided if he had used his power, but he refused to do so.

If the person being questioned is compelled to answer then how far does it go? Do they have to give the whole truth or can they get away with half truths? In a lot of books and shows where a character cannot (or will not) lie then lies of omission are seen as an acceptable loophole.

As others have pointed out, the truth can mean different things to different people. People forget important details, believe lies that others have told them or simply misremember things. It might be interesting to consider something like the Mandela effect, where a group of people will remember something differently to how it actually happened.

 

For your villain you can have someone who always tells the truth. In DND terms because this came up quite a bit once- I was paying a Lawful Evil along side a paladin who would cast "zone of truth" a lot (not specifically on me.. its an area so even the paladin is in it) when questioning others. But my Lawful Evil never resisted the zone and never changed anything he would have said anyway- as he never knowingly lied as a rule. He always kept his word and never had anything to hide as he felt justified and correct in all his actions. he was a dangerous guy and a good villain/hero.

I do like the idea that your protag has one person that is quite a bad person- but they never lie, so his power does not work on them, and consequently... they are the only person the hero can actually trust while many firends and 'good people' they cannot.

 

Side effects ideas- They cannot lie, they only get to ask two or three questions of a person then it never works again on them, they can only use the power two or three times a day, each time they se the power they become more sleepy, they receive a cut or burn every time they use the power, they lose a memory each time.

 

Well, it could be that the TRUTH does not exist, but only the truth. In that case, the truth is a combination of what the questioner believes is the truth and what the one answering believes is the truth. Change SuperA to SuperB and the idea of truth changes, which changes the answer you get.

A good question here is that you should determine what the answer to a philosophical question would be. Say SuperA and SuperB both ask: "What is the meaning of life?" What answer would you get? There are a few possible answers, which dramatically change how the power works:
- You get the ONE AND ONLY true meaning of life (aka 42...).
- You get what the person being questioned considers the meaning of life to be.
- You get what the Super considers to be the meaning of life
- You get a blend of what the Super and the person being questioned consider the meaning of life
- You get no answer at all, since it doesn't exist

If you want another direction in which you could take this. Then what if you never get a straight answer, but you get prophetic / riddles as answers? If you can always interpret the answer in multiple ways, then it becomes a much more dangerous power to use.