Vicious Stomp

(Combat)
You take advantage of the moment to brutally kick an enemy when he is down.
 

Prerequisites

Combat Reflexes, Improved Unarmed Strike.
 

Benefit

Whenever an opponent falls Prone adjacent to you, that opponent provokes an attack of opportunity from you. This attack must be an unarmed strike.
 

Combat Trick

If you have a Stamina pool, the following Combat Trick may be used with this feat.
  When an opponent provokes an unarmed strike attack of opportunity from you by Falling Prone, you can spend 2 Stamina points to deal an additional 1d6 points of damage with that unarmed strike.