Easiest way to incapacitate and even kill someone is to grab them by the shirt or hair and let their attack on you lunge them towards you while you use your hand between the thumb and forefinger to smash their throat, crushing their larynx. Easy and very effective.
If you’re gokng todo ghat, easier to use heel of the hand, or middle knuckles.
I didn’t want to go into specialized kill punches...not something people need to know unless you KNOW they will not use that information for less than honorable purposes. I know a couple of other one punch kill shots, I do not tell those, I swore I would keep it confidential, unless I can be sure the recipient does not intend to use it for criminal purposes or as a bully.
Thousands of common thugs would love to know how to easily take out an adversary...say, someone who looked at his girlfriend twice...you have to be careful who knows that kind of thing. So I never let those out.