He Will Slay You with His Tongue

Prompt fill for Daddymort Fest 2023:

"Harry distracts Voldemort (without thinking) by calling him "Daddy" in the middle of the battle in Parseltounge. It works and Voldemort loses his mind. People ask him what he said but he is too ashamed to admit it, only that "hey it worked." Harry's comments keep getting filthier and filthier when they fight until Voldemort can't take it anymore."