Walking Ballista + Unspeakable Symbol + City on Fire Combo

All permanents on the battlefield.

You have a way to give Walking Ballista lifelink. Walking Ballista has at least two +1/+1 counters on it, or your life total is at least 4.

Give Walking Ballista lifelink, if needed.

If Walking Ballista has less than two +1/+1 counters on it, activate Unspeakable Symbol by paying 3 life, putting a +1/+1 counter on Walking Ballista.

Activate Walking Ballista's second ability by removing a +1/+1 counter from it, dealing 3 damage to an opponent or a permanent an opponent controls, and causing you to gain 3 life.

Repeat from step 2.

Infinite damage

Infinite lifegain triggers