Blightbeetle + Goblin Bombardment + Stiltzkin, Moogle Merchant

Blightbeetle

Goblin Bombardment

Stiltzkin, Moogle Merchant

How it works

1. Donate Blightbeetle to an opponent
2. Activate Goblin Bombardment by sacrificing the undying creature.
3. When the undying creature dies, its undying ability triggers, returning itself from your graveyard to the battlefield without a +1/+1 counter on it due to Blightbeetle.
4. Resolve the Goblin Bombardment ability.
5. Repeat from step 2.

This clever loop turns an opponent's own defenses against them by utilizing Blightbeetle's passive static ability, which ensures that no creature your opponents control can ever receive +1/+1 counters. With that restriction in place, any creature you control with undying that has been donated to your opponent via Stiltzkin, Moogle Merchant's activated ability will return from the graveyard completely counter-free whenever it perishes. You can then feed these endlessly recurring creatures to Goblin Bombardment to repeatedly sacrifice them, generating an inexhaustible storm of death triggers and lethal damage.