Can Bellows Breath target the same unit 3 times?

No, Bellows Breath cannot target the same unit multiple times with a single instance of the spell.

According to the RiftJudge FAQ #168 and #1871:

• Bellows Breath deals 1 damage to up to three different units at the same location. Each target must be a distinct unit.
• You cannot choose the same unit multiple times to deal 3 damage to it with one cast.

Important Nuance: Using "Repeat"

While a single instance of the spell cannot target the same unit more than once, if you pay the Repeat cost, you are executing the effect a second time.

As clarified in RiftJudge FAQ #8454 and #1306:

1. Targeting: The first instance of the spell targets up to three different units. The second (repeated) instance is a separate execution of the effect, which allows you to target the same unit again.
2. Resolution: If you target the same unit with both the first instance and the repeated instance, it will take 1 damage from the first and 1 damage from the second, for a total of 2 damage.
3. Survival: Damage is marked on a unit but does not reduce its Might. Lethal damage is only checked during Cleanup, which occurs after the entire spell (including the repeated instance) has finished resolving. Therefore, the unit will not be defeated until the spell is fully resolved.