Mindfire
Istar
I know it's generally poor storytelling to make a villain evil just because evil. But what if it was played for laughs in a kind of dark way? Like there's this card-carrying villain who boasts and brags about how evil he is and how much he enjoys being evil, but really he only does it because he gets a kick out of rebellion, discord, and trolling society at large. Then one day he accidentally summons a powerful demon and gets a taste of what real evil is and it scares him straighter than a yardstick. (Or drives him gibbering mad.)