Sephiroth, Planet's Heir has a +1/+1 counter on it.
Steps
If needed, give
Sephiroth deathtouch.
Activate
Sephiroth using
Triskelion's ability by removing a +1/+1 counter from it, dealing 1 damage to a creature an opponent controls and destroying it due to
Sephiroth's deathtouch.
When the creature dies,
Sephiroth triggers, putting a +1/+1 counter on it.
Repeat from step 2.
Notes
If the method used to give
Sephiroth deathtouch is repeatable and/or indefinite, you may repeat this loop on subsequent turns. You may also repeat this loop whenever a creature enters the battlefield under an opponent's control.
Results
Destroy all creatures that enter the battlefield under an opponent's control.