Can you counter Bellows Breath with Defy if it's repeated?

Yes, you can counter Bellows Breath with Defy even if the Repeat cost has been paid.

According to the official FAQ and game rules:

1. Defy checks Base Cost: Defy only cares about the base energy and power cost of the card on the chain. Since Bellows Breath has a base cost of 1 Energy and 1 Power, it remains a legal target for Defy regardless of whether additional costs (like Repeat) were paid.
2. Repeat is not a separate spell: Paying the Repeat cost does not create a second copy of the spell or a new item on the chain. Instead, it modifies the existing spell to execute its instructions a second time upon resolution (Rule 746.1.d).
3. Countering stops the whole effect: When a spell is countered, it does nothing and is placed in the trash (Rule 412.1.a). This stops the entire spell, including both the initial effect and the repeated effect.

Relevant Ruling:

"Yes, a card with Repeat can be countered by Defy even when being repeated, because Defy only cares about the base cost of the card. When Defy counters the spell, it stops the entire spell including the repeat effect."