Killgrave, The Purple Man

Power Up (Whenever this creature deals combat
damage to a player, if it does not have a +1/+1
counter on it, put a +1/+1 counter on it.)
{t}, Remove a +1/+1 counter from this creature:
Gain control of target creature for as long as you control Killgrave and Killgrave remains tapped.
You may choose not to untap Killgrave during
your untap step.