Stalwart Successor + Wingrattle Scarecrow + Yahenni, Undying Partisan

Stalwart Successor

Wingrattle Scarecrow

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Wingrattle Scarecrow
2. When Wingrattle Scarecrow dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Wingrattle Scarecrow enters, Stalwart Successor triggers, putting a +1/+1 counter on Wingrattle Scarecrow
4. Resolve the Yahenni ability.
5. Repeat.