Bloody Brawl

Creatures can only have one +1/+1 counter, if a creature has two or more +1/+1 counters on it remove all +1/+1 counters on it.
{b}{b}, {t}, Sacrifice a creature: Distribute X +1/+1 counters on any number of target creatures, where X is the sacrificed creature's toughness.
So many people die in battle, and those deaths just help to encourage the massacre.