Seductive Thief

{1}{u}{t}: Tap target creature an opponent controls. It doesn't untap on its controllers next untap step.
{1}{b}{t}: Target tapped creature gets a -1/-1 counter and Seductive Thief gets a +1/+1 counter.
{3}{b}{t}: Target tapped creature gets a -2/-2 counter and Seductive Thief gets a +2/+2 counter.