Cast Strength of Will by paying {1}{G}, targeting Walking Ballista.
Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to it.
Walking Ballista triggers, putting two +1/+1 counters on it due to Hardened Scales.
Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to any target.
Repeat from step 2.

Infinite damage

Infinite +1/+1 counters on a creature

Strength of Will

Hardened Scales

Walking Ballista

Cast Strength of Will by paying {1}{G}, targeting Herd Baloth.
Put a +1/+1 counter on Herd Baloth.
Herd Baloth triggers, creating a creature token.
When the creature token enters, Warstorm Surge triggers, dealing damage to Herd Baloth.
Herd Baloth triggers, putting a +1/+1 counter on it.
Repeat from step 3.

Infinite creature ETB

Infinite creature tokens

Warstorm Surge

Herd Baloth

Cast Strength of Will by paying {1}{G}, targeting Spike Feeder.
Activate Aetherflux Reservoir by paying 50 life, dealing 50 damage to Spike Feeder.
Spike Feeder triggers, putting fifty +1/+1 counters on it.
Activate Spike Feeder's second ability 25 times by removing 25 +1/+1 counters from it, causing you to gain 50 life.
Repeat.

Infinite lifegain triggers

Infinite lifegain

Spike Feeder

Aetherflux Reservoir

Combos with "Strength of Will"