Mundyr, Soul of the Wild

Trample, menace, haste
Mundyr, Soul of the Wild enters the battlefield
with seven +1/+1 counters on it. Whenever a
creature you control with 4 or more power attacks, proliferate, then proliferate again. (You chose any number of permanents and/or players with counters on
them, then give each another counter of a kind already
there. Then do it again.)
When the ancient woodlands came under threat, it sent
its greatest champion.