[NineDaysDead]

This might be useful:

Originally Posted by Kromm

I'd call it a Stamp Kick (Martial Arts, pp. 80-81), which defaults to Brawling-3 or Karate-3. Here, specifically, I'd allow a default to DX-3 or Acrobatics-3 as well. This would certainly be subject to Attack from Above (p. B402): an extra -2 to hit and an extra -2 to the victim's defense. A hit normally does thrust+1, plus skill bonuses. I would replace thrust with the attacker's base falling damage, if higher, before adding the +1 or any bonuses.

As for damage sustained by the attacker, I would use normal falling damage. I absolutely would permit Acrobatics to reduce this without reducing damage to the victim – a valid tactic for dissipating the energy of a fall is to deposit it in whatever you land on, after all. And as has been pointed out, there's no special need for symmetry here – generally, the attacker is control of the body part used to strike, what it hits, and how force is concentrated. I would, however, look at the "if you miss or your target successfully defends, you fall unless you can make a DX-8 or Acrobatics-4 roll" rule from Flying Jump Kick. I think I would give -4 to any Acrobatics roll the attacker makes to reduce damage if the kick fails to connect for any reason.

I wouldn't absolutely require All-Out Attack (Strong) or a shout of "Banzai!", "Geronimo!", or "Kowabunga!", but it sure seems to fit.