Grendel

Hexproof, trample
Enrage — Whenever Grendel is dealt damage,
put two +1/+1 counters on it. (It must survive the damage dealt)
When Grendel attacks, you may have it fight
target creature the defending player controls.
If the target dies as a result of the damage
dealt by Grendel in this way, you may repeat
this process.