Berserker has seen enough. The pure fury crystallizes into cold action. No need to snap his neck if he can hit him hard enough in the chest -- a single, sharp strike can disrupt the heart rhythm enough to stop it. His strength is comparable to when it was as a Servant, even, so it's something he can manage. The dragon takes a few steps forward as if to inspect Waver, then turns his attention to the seller.

"I'll keep that in mind."

He punches him hard in the chest, just once and with a significant amount of force. Commotio cordis can look like a heart attack and since there's no witnesses in this corner of the bazaar other than the monsters he's selling, it's plausible. Free the others along with Waver and gets them to the underground. He knows the way thanks to Geralt, but he needs to get them free first.

"Waver. Can you hear me?"