Your unarmed strikes become as sharp as blades.
Prerequisites: Str 23, Wis 23, Improved Critical (unarmed strike), Improved Unarmed Strike, Stunning Fist, ki strike (adamantine).
Benefit: The character’s unarmed strike has a critical threat range of 18–20 and deals slashing damage (at the character’s option any attack can deal bludgeoning damage, but cannot then take advantage of the enhanced threat range). This ability doesn’t stack with other abilities that expand that character’s unarmed strike’s threat range.
Source: Standard Reference Document under Open Game License v1.0a, which updated this feat originally published in the Epic Level Handbook, page 61.