Nero

Nero is a fallen human who was forced to live in the Demon Realm after asking the Demons to give him powers to get revenge. At first, he was upset about it, but soon he became more corrupted and now he doesn't mind being there. Him being corrupted changed his appearance to where he has one eye with inverted colors of his regular one, and he has black markings on his arms that take up more space depending on his state of mind. He also changes from being completely evil to generally kind quickly as a side-effect of being corrupted.