Sasuke.
-When he was 8 years old, he lost everyone. The most important person to him, Itachi was the one who made Sasuke's life a living hell. Just a little before the massacre, Sasuke got respect from his father, which makes it even sadder. Sasuke even had to see his Clan getting slaughtered, because of Itachi's Tsukiyomi.
The only thing Sasuke could think about was getting vengeance against his brother and he broke his every bond in order to do that. Finally he gets his long waited revenge, but that made it even worse. It turns out that the reason why Itachi didn't kill Sasuke was because Itachi loved him. Not only that, The Uchiha Clan got killed because of Konoha.