Activate Triskelion by removing a +1/+1 counter from it, putting two +1/+1 counters on it due to Vigor.
Activate Triskelion by removing a +1/+1 counter from it, dealing 1 damage to any target.
Repeat as desired.

Infinite damage

Infinite +1/+1 counters

Vigor

Triskelion

Sawhorn Nemesis

Activate Anti-Venom using Walking Ballista's ability by removing a +1/+1 counter from it, targeting itself and putting two +1/+1 counters on it due to its replacement effect and Sawhorn Nemesis.
Activate Anti-Venom using Walking Ballista's ability by removing a +1/+1 counter from it, dealing 1 damage to any target.
Repeat.

Infinite +1/+1 counters on a creature

Anti-Venom, Horrifying Healer

Agatha's Soul Cauldron

Walking Ballista

Activate Deathbringer Thoctar by removing a +1/+1 counter from it, putting two +1/+1 counters on it due to Vigor.
Activate Deathbringer Thoctar by removing a +1/+1 counter from it, dealing 1 damage to any target.
Repeat as desired.

Combos with "Sawhorn Nemesis"