Stalwart Successor, and Yahenni, Undying Partisan

Prerequisites

• Stalwart Successor on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni by sacrificing the creature with persist
2. When that creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. When that creature enters, Stalwart Successor triggers, putting a +1/+1 counter on it
4. Remove a +1/+1 and a -1/-1 counter from that creature as a state-based action
5. Resolve the Yahenni ability
6. Repeat

Results

• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers