Arthas
The former Prince of the kingdom of Lorderan and Paladin of the Silver Hand in the rts game Warcraft 3. In order to save his people from dying at the hands of a plague of undeath, he:
*Killed the entire populace of the city of Stratholme

*Killed his best friend and fellow hero Mauradin Bronzebeard just for a sword to kill the guy who made him kill all those people in Stratholme.

In the end, however, he became a stooge of the very source of the undead plague, the Lich King. He became an anti-paladin, a death knight, and soon took over the kingdom he was destined to rule anyway, but soon lost it because he was too busy trying to kill a whiny emo Nelf-demon (See Illidan) that his powers waned and a superhot undead elf chick (See Sylvanas Windrunner) took over Lorderan.
ZOMG!!!!11!1!11 I cant w8 to kill Arthas, ill be soooo uber! :P