Blightbeetle + Bloodflow Connoisseur + Coveted Falcon

Blightbeetle

Bloodflow Connoisseur

Coveted Falcon

How it works

1. Activate Coveted Falcon by paying 1, turning it face up.
2. Coveted Falcon triggers, causing an opponent to gain control of Blightbeetle and causing you to draw a card.
3. Activate Bloodflow Connoisseur by sacrificing the undying creature.
4. 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.
5. Resolve the Bloodflow Connoisseur ability.
6. Repeat from step 3.

This clever loop sets up an eternal cycle of sacrifice and return by exploiting a clever rules interaction. While Bloodflow Connoisseur stands ready to devour creatures and grow with every sacrifice, Blightbeetle's static ability ensures that any creature returning via undying completely ignores its usual +1/+1 counter restriction, allowing it to die over and over again. Meanwhile, Coveted Falcon acts as the political linchpin; by turning it face up, you gift Blightbeetle to an opponent (since you technically own it), ensuring their board stays locked out of +1/+1 counters while you continuously rake in death, enter-the-battlefield, and leave-the-battlefield triggers.