Ambitious Backstabber

First strike, promote (Whenever a creature you control leaves the battlefield, if that creature had greater power or toughness than this creature, put a +1/+1 counter on this creature.)
{0}: Destroy target creature you control. You may activate this ability only once per turn.
"I can appreciate its initiative. Doesn't mean I'm going to recruit it though."
-- Lorius of the Revellers