How do you do a karate punch?

A very wide, looping punch intended to throw as much bodyweight as possible behind a punch. Can cause a KO if it connects, but this depends on your own power, the ability of the man in front of you to take a punch, your accuracy (no use if you punch the cranium), and the structural integirty of the punch - i.e. if you make a bad fist and your wrist isn't straight, you're just going to hurt yourself.