That is a
flying side kick a difficult to master Tae Kwan Do kick. It is probably the most forceful attack you can make measured by total impulse delivered to the target. It is designed to crack ribs and break bones. Arnold is obviously in much better shape than anticipated because he could have been left crippled by that attack.
Short of the deserved eye for an eye justice the perp needs to be jailed for a couple of decades.