Not sure this may have already been answered somewhere?

Anyway. I'm playing Black Panther. If an enemy attacks me I retaliate 1. But what if I use an ally to defend the attack? Do I still retaliate or as the attack is defended by another character is retaliate nullified?

That's been clarified in the newest version of the Rules Reference, p. 21:

Quote

BL ACK PANTHER (CORE SET, 40A)

Q: If an enemy initiates an attack against Black Panther but another hero or an ally defends against that attack, will Black Panther’s retaliate ability trigger?

A: No. Black Panther himself must be attacked for retaliate
to trigger.

Thanks.