Board Thread:General Discussion/@comment-26006155-20190820122909/@comment-26006155-20190911003441

Sans dunking Frisk is also a special case.

This is a Betrayal Attack.

Whenever Frisk pacifies a boss, so it’s ready to be spared, then chooses to attack again instead, it’s always a one-shot KO. And has special animations from Toriel, Papyrus, for example.

The only other creature in Undertale who can perform a Betrayal Attack is Sans.

You already know why I think this is.