Gaara:
-Originally because of how much of a lunatic he was.
-Now, like then, how he seems totally unphased by any opponent, which just goes hand and hand with badassery.
-Him realizing the error in his ways, thus setting aside hate to strive for acceptance, ultimately rising to the ranks of Kage
-Saved his village at the cost of his own life
-All in all, he played both roles to perfection, antagonist, as well as a supporting/side character