Nightcrawler

Trample
{b}{b}{t}: Tap target creature. As long as you control Nightcrawler, tapped creature does not untap during its controllers untap step and at the beginning of your upkeep, place a -1/-1 counter on creatures tapped this way. Put a +1/+1 counter on Nightcrawler whenever a -1/-1 counter is put on a creature this way.