Young Wolf dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the
Goblin Bombardment ability.
Activate
Goblin Bombardment by sacrificing
Young Wolf.
When
Young Wolf dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Young Wolf enters and dies as a state-based action due to having 0 toughness. Its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the
Goblin Bombardment ability from step 4.
Repeat from step 4.
Notes
If
Young Wolf starts with a +1/+1 counter on it, then you may start the combo from step 4 instead.
Results
Infinite ETB.
Infinite LTB.
Infinite damage.
Infinite death triggers.
Infinite sacrifice triggers.
Metadata
In 2 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).