At Void Gate, how much damage does a repeated bellows breath do

2 damage per instance — so a repeated Bellows Breath deals two separate 2-damage hits (4 total to a single unit targeted both times).

Void Gate's 1 Bonus Damage applies to each instance of damage (Rule 715.2: bonus is added to each target separately). Bellows Breath's Repeat executes the "Deal 1" instruction a second time, so each execution becomes "Deal 2" to up to three units at that location. Targeting one unit with both executions leaves it with 4 damage marked, but as two 2-damage events, not a single 4-damage hit — no cleanup or healing happens between them.