Infinite Damage with Walking Ballista and Vraska

Step 1: Cast Walking Ballista with at least two +1/+1 counters on it.

Step 2: Use Vraska, Swarm Eminence's ability to create a 1/1 Assassin token whenever a creature with deathtouch you control deals damage.

Step 3: Use Aveline to continuously create tokens that can trigger Vraska's ability to generate more +1/+1 counters on Walking Ballista.

Step 4: Remove +1/+1 counters from Walking Ballista to deal damage to any target, triggering Vraska's ability again if needed.

Step 5: Repeat the process to deal infinite damage.