The Unending Fury

Haste, Double Strike
Unless you control Richter, Cold Warrior, The
Unending Fury attacks each turn if able.
At the beginning of your end step, if The
Unending Fury didn't deal combat damage to a
player or deal damage to any creatures that left
the battlefield this turn, place 3 +1/+1 counters
on it.
"Who let that... thing... out?"
—Richter, Cold Warrior