The Great Goblin + The Red Terror + Leyline of Transformation
The Great Goblin
The Red Terror
Leyline of Transformation
Infinite +1/+1 counters on a creatureInfinite damage
How it works
Put a counter on The Red Terror.
The Great Goblin's first ability triggers, as The Red Terror is a Goblin, Orc or Army due to Leyline of Transformation, dealing 2 damage to an opponent.
The Red Terror triggers, putting a +1/+1 counter on it.