Bane

Bane enters the battlefield with X +1/+1 counters on it.
{g}{g}: Put a +1/+1 counter on Bane.
{b}{b}, {t}, Remove all +1/+1 counters from Bane: All other creatures get -X/-X until end of turn, where X is the number of +1/+1 counters removed this way.
Power. Venom. Rage.