Video Game Trick 172: Killer Instinct (SNES) - A.I. Stupidity 4 (w/Eyedol, on 6-Star) - Part IV 

You have to do the stomp move first (which is done by pressing Back, Back, Medium Punch (or Y, if the controller settings are already at default settings)). Then you have to press Quarter-Circle Forward, Fierce Punch (X in the default settings) during his stomp animation.