i had a hard time understanding what you are trying to accomplish but i think i know what you need.
you want to be able to "kill" your enemy's or bounce off them when your player collides with them from above?
if yes try this:
create a square box(sprite) that has almost the same size as your character.
set to invisible from properties and then give it the platform behavior.
delete the platform behavior from your character.
set:
every tick set position to another object your new square sprite to your player.
now you move your square and the player moves along.
square on collision with enemy and
platform is falling------------------------------------------- set square platform vector y to -500.
thats it! your player now bounces off enemy's.