10. Seifer (Final Fantasy VIII)
Seifer is a total douche for the most part of the game. He constantly torments you and the gang even before he joins the "dark side." On top of that, he was even willing to offer Rinoa, his ex-girlfriend's, body to Ultimecia as a new host. However, the epilogue does suggest that he saw the error of his ways.
I kind of feel sorry for him. Why? Well, I think that he was horribly misguided by his "romantic" dream to be sorcerer's knight. At the same time, I think that he was helping Edea because he remembers her as Matron from the orphanage at some point if I'm not mistaken. He also showed remorse at one point, but said that it was too late for him to go back.