Colossal Snowman

When Colossal Snowman enters the battlefield, remove all -1/-1 counters from all creatures. Put a +1/+1 counter on Colossal Snowman for each counter removed this way.
Colossal Snowman can't be blocked unless all creatures defending player controls block it.
Dismember, dismember. (If a creature has multiple instances of dismember, each trigger separately.)