Blightbeetle + Bloodflow Connoisseur + Zedruu the Greathearted

Blightbeetle

Bloodflow Connoisseur

Zedruu the Greathearted

How it works

1. Donate Blightbeetle to an opponent
2. Activate Bloodflow Connoisseur 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 Bloodflow Connoisseur ability.
5. Repeat from step 2.

This clever loop turns Blightbeetle's passive hate into the engine of an infinite sacrifice loop, using its clause that prevents opponents' creatures from getting +1/+1 counters to subvert the normal restriction on undying. By donating Blightbeetle to your opponent with Zedruu the Greathearted's activated ability, you set the stage for your own creature (referenced in the loop) to repeatedly die and return without accumulating counters. Each time it returns, Bloodflow Connoisseur is there to eagerly sacrifice it again, growing larger with infinite +1/+1 counters while generating endless death, ETB, and LTB triggers to fuel your strategy.