Stalwart Successor + Lesser Masticore + Yahenni, Undying Partisan

Stalwart Successor

Lesser Masticore

Yahenni, Undying Partisan

How it works

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