Yahenni, Undying Partisan + Yuna, Grand Summoner

Yahenni, Undying Partisan

Yuna, Grand Summoner

How it works

1. Activate Yahenni by sacrificing the persist creature that has a +1/+1 counter on it.
2. When that creature dies, its persist ability and Yuna trigger.
3. Resolve Yuna's ability, putting at least two +1/+1 counters onto the surviving persist creature due to the counter-increasing effect.
4. If that creature had a -1/-1 counter on it, remove that and one of the +1/+1 counters from it as a state-based action.
5. Resolve the persist ability from step 2, returning the persist creature from your graveyard to the battlefield with a -1/-1 counter.
6. Resolve the Yahenni ability from step 1.
7. Repeat.