After one has seen this clip, it's hard to argue that the circular punch doesn't generate enough knock down power.
Some people would call this a hook, and maybe a "long hook" but it isn't. A closer look shows that he's not using the same knuckles that are used when throwing the modern hooks that we see in boxing and in other systems. Here's what I see. I could be wrong on this stuff, in terms of the guy that gets knocked out.
1. The attacker tries to pull tries to pull down the guard hand.
2. The defender evades the "lead hand guard pull" and uses that momentum to power a circular long fist. The being of the punch and the escape from the "lead hand guard pull" are the same. (2 things at the same time powered by the same motion.)
3. Missing the "lead hand guard pull" causes that delay in reaction that I was speaking of. When I look at his left arm, it seems to retreat in limbo and not back into chamber. His guard pull travels across his body instead of downward. Had he pulled his hand downward he would have been able to use that momentum in a circular motion to return the hand to cover his head. But because his pull goes across his body, it travels longer than needed and delayed his punching mechanics of the right arm (tried to make my hand move in a similar manner and I found that I was unable to punch with my right hand with any speed. The body mechanics were broke.
4. The attacker sees the counters punch and turn his head. In order to slip the punch my slightly moving his face. (it's about all he had time to do), which goes back to what I was saying about (only having enough time to make a face in preparation of getting hit.)
5. The turning of the head kills his field of vision. By turning his head like that, the defenders punch will travel in the blind spot with no problem . This is an easy thing to test. Place a bottle, or object in front of you. Now turn your head about 50 degrees to the right or left and you'll see that object turns into a haze and almost vanish.
here you can see how this punch is traveling in the blind spot. At this point the brain isn't going to be able to process the punch because it's no longer getting visual data about the punch
This is confirmation that the punch traveled in the blind spot. It hits him right were the ear and Jaw hinges. He would have never seen this punch coming. We also don't see the attacker counter with faster right punch.
As far as long fist punching techniques. This punch landed right where it was supposed to. Text book example.