Angel (Buffy)

Angel is one of the main heroes of the Buffy the Vampire Slayer franchise and even spawned his own series and merchandise. Originally a villainous vampire called Angelus, Angel became a hero via a curse put upon him by Gypsies that gave him a soul, which led to him becoming a defender of the people he once preyed upon - though there have been many times that Angel has had to face his darkness and he constantly walks the thin line between good and evil as one of the few vampires in the Buffy universe who has a soul.

Trivia

 * He's the only character to have appeared in the unaired Buffy pilot as well as the Buffy and Angel's series premiere and series finale episodes.