Jaime Lannister (Nickolaj Coster-Waldau), Game of Thrones
The Kingslayer earned his nickname by betraying and murdering his liege lord. Even worse, he carried on an incestuous relationship with his twin sister and then flung a child out of a tower window when he caught them in the act. In Season 3, however, we discovered Jaime's hitherto unknown noble side. It turns out that he saved lives by killing the mad king, who had planned on burning the city of King's Landing and all of its citizens. Also, Jaime's respect for Brienne of Tarth prompted him to save her from a death by bear-mauling. From our standpoint, it seems that really, he's been led astray by his heart and a very ambitious twin sister. And say what you will about that relationship, but at least he's been unwavering loyal to her. Cersei doesn't deserve him.