If a reaction triggers when an ally is attacked and gives you a free attack against the attacker and you kill the attacker, does the triggering attack still deal damage? Is there a page number you can point me to that details the answer?
The Paladin’s Retributive Strike definitely requires it (because it triggers on damage dealt), but I’m curious on the overall general principle.
Retributive Strike specifically says "damages your ally" so the damage is already done. I don't know of another ability that would interrupt in a similar manner, though.
If there is, I'd have to examine its wording.