Rite of Passage + Walking Ballista + Doc Samson, Super Psychiatrist

Rite of Passage

Walking Ballista

Doc Samson, Super Psychiatrist

How it works

1. Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to itself.
2. Rite of Passage triggers, putting two +1/+1 counters on Walking Ballista.
3. Repeat an arbitrarily large number of times.
4. Move to the next turn, removing all damage marked on Walking Ballista.
5. Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to any target.
6. Repeat step 5 as desired.