[quote=@Ciaran]
Challenge accepted.

Ricky Hatton's (pro boxer) punch speed - ~25mph
Diameter of a H2O molecule (most common molecule in human skin) - ~0.29nm (0.000000029mm)
25mph = 11176000000nm per second
Deceleration = (0 - 11176000000nm per second)/0.00000000025948461 seconds = -4306999200000000000000000000nm per second per second.
-4306999200000000000000000000nm per second per second = -430699917039m per second per second, or -430699917.039km per second per second.
(If you don't want to read that brick of a number, that's over 430 million kilometres.)
-430699917039m*0.7 (average mass of a human fist) = 301489941927N
(Or three-hundred thousand million Newtons of force.)

So how much is ~300,000,000,000 Newtons of force? Well...[list]
[*]About 3300 Newtons will break a rib.
[*]About 250,000 Newtons will instantly stop a car moving at 60mph (depending on the car).
[*]About 750,000 Newtons are necessary for a rocket to lift off.
[*]A 50-kiloton nuke delivers about 450 million newtons of force.
[*]And since I'm running out of ideas, it would take about a 34 megaton nuke directly hitting this person's fist to re-create the damage that one punch would cause to them.[/list]
[/quote]

Well now I know who to come to with crazy character powers. 

In my multiverse a character hits a cannon shot back to the spaceship firing it as if a baseball, and said cannonball tears completely through it with enough power to destroy the small city that was its intended target. So...I'm guessing deflecting low kiloton level power back to sender would be even more drastic than that ability, but not sure. Whatever the case I know logically the shockwave would destroy everything anyways but I still want to keep the scene in for coolness factor. I don't think I'm taking shockwaves into account for much of any battle as they can fight without destroying surroundings unless that's their intent.