Putrid Goblin + Yahenni, Undying Partisan + Hardened Academic

Putrid Goblin

Yahenni, Undying Partisan

Hardened Academic

How it works

1. Activate Yahenni by sacrificing Putrid Goblin.
2. When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Hardened Academic triggers, putting a +1/+1 counter on Putrid Goblin.
4. Resolve the Yahenni ability.
5. Repeat.