Activate Goblin Bombardment by sacrificing the undying creature.
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.
Resolve the Goblin Bombardment ability.
Repeat from step 2.
This clever loop transforms a mechanical anti-counter safeguard into an infinite engine of destruction. By using **Donate** to hand your opponent **Blightbeetle**, its static ability ensures that any of your creatures with undying can never receive the +1/+1 counters that normally prevent the mechanic from repeating indefinitely. This allows you to repeatedly feed your creatures to **Goblin Bombardment**, sacrificing them for damage while they endlessly loop back from the graveyard without their usual limitations.