Apprentice of Villain

Heroes that served as an apprentice to a villain at any point of their lives. These heroes may have been forced to be an apprentice to a villain under some certain circumstances, not aware that their mentors are villains or simply lost their way.  When they find out their mentor is evil, or when they realize the path they are on is the wrong one, the hero abandons their master, which will most likely lead to a confrontation between teacher and student.