pf2e.fyi
From Pathfinder Lost Omens Tian Xia Character Guide, which isn't enabled.

Echoing Violence

FEAT 18
ARCHETYPEDEATHINCAPACITATION
Activity free action
Archetype Martial Artist
Prerequisites Martial Artist Dedication
Frequency once per minute
Trigger You critically succeed with an unarmed Strike against an opponent.

Your powerful attack causes damage that reverberates through your opponent's body, shaking muscle from bone. The creature takes 10d6 bludgeoning damage with a basic Fortitude save against your class DC. If it critically fails, it immediately dies as your blow tears apart its body internally.

Pathfinder Lost Omens Tian Xia Character GuideORC