Put it at the end of the boast, as the reply that closes the argument, then follow it with the Fail Sound Meme to underline the defeat. For a slower build, open with It Was At This Moment He Knew before the claim, then let this clip answer it.
About this sound
This four-second clip is King Théoden's stern line telling Gríma Wormtongue he has no power in Meduseld, delivered with final authority. It feels satisfyingly blunt and triumphant, like watching a false authority collapse in one sentence. It comes from The Lord of the Rings: The Two Towers.