you mean stomp action? like mario jumping on mushroms?
if your using platformer behavior for jumping and control... u can easy do this by adding 2 conditions on colision with enemy and detect if the main player is above the enemy... so the conditions wold be
1 on collision with enemy
2 is mainplayer falling ...
action destroy enemy
it may not work properly ... but the main idea is to calculate the main player position when he is above ... also if u using platformer behavior.. the only way you can make things solid, so the main actor can behave, like he hit something solid is by adding the solid behavior to other things in game...
i think there is a platformer example around forum also.. doing exactly those things. ..