The one that you can throw properly and at the right time to do the goal desired. Not every punch is meant to be a knockout blow, the jab is a very useful punch and is most commonly used but rarely ever is someone dropped from it. Each punch has it's own purpose and the question is which one can you use at the proper time for the right purpose.

Every fighter is different. The best punch is dependant on how you train, and what punch you can best acheive.

I teach my early fighters to hammerfist, because it's the hardest punch to screw up, and is least likely to lead to self injury. This means that an early student can hit the hardest and mostconfidently with the hammerfist, a very basic and primal motion.

As they advance, the best punch is different for everyone.

I would overall say it would be the hook punch.

But not just the karate style or muay thai style hook.

The hook should use the power of your full body rotation.

So you should spin your body into the punch. As the body rotational torso almost triples the amount of force rather than just punching using arm strength, the hook can make use of the body rotation the best.

It is also good because it makes the brain hit the side of the skull causing unconciousness. The jab or upper cut rather damages the skull rather than knocking the person out.

But i like the jab as well becaues it is very damaging

a clean hard chin shot or punch to the liver will take out anyone. How that punch is delivered is whatever works for you.

In my experience, the Gyacku zuki, reverser punch when power is from the hips. Very effective punch.

The punch that does the most damage, but is also the hardest to land is an uppercut.

Any punch technique that you are truly comfortable in executing.

“I fear not the man who has practiced 10,000 kicks once, but I fear the man who had practiced one kick 10,000 times.”

― Bruce Lee

The Jab.

The one you land effectively

To the throat...

The one you can land effectively.