Riddler (Batman) - After suffering brain damage, Riddler seemingly loses his villainous tendencies but maintains his intellect. Due to this, he chooses to reinvent himself as a private detective (ala someone like Hercules Poirot) and ends up assisting with a few different murder investigations alongside Batman until eventually returning back to his old ways and becoming a villain again.

Garmadon (Ninjago) - Garmadon gets freed of the curse that turned him evil at the end of season 2, leaving him as a more morally good version of himself. As a result, for the new two following seasons he attempts to reinvent himself as a teacher alongside Master Wu and making right his previous actions, assisting and guiding his son along the way and being a better father. He ultimately ends up dying sacrificing himself at the end of Season 4, with it taking until the 8th season for him to be revived again, this time fully as a villain with none of his previous empathy

Magneto (X-Men 97) - At the request of a once dying but recovered Professor X, Magneto is tasked in his will to lead the X-Men in his stead, acting towards Xavier’s goal of coexistence, despite Magneto’s previous misgivings towards humanity. Magneto, while almost willing to give into his anger, chooses to follow Xavier’s example and genuinely makes an effort to act more akin to the rest of the X-Men in combating issues and is at a point where he is able to come to peace with himself….until Genosha gets attacked by sentinels, leading to many mutants being killed and himself being tortured by the villain behind the event Bastian. While Magneto is able to escape and eventually does help the X-Men again later, he returns back to his old ways and claims humanity is not worth protecting.

Villain actually has a redemption where they actually end up becoming part of the supporting cast and help the hero for a while before returning back to evil