>>19992That guy got knocked out because the lower part of the back of the head is very susceptible. But you can do that with a hook-punch which is less risky.
The second guy in the video used a fancy spin kick, which is very risky. It's easy to block (just keep the elbows up) and usually ends with a knee in your groin and loosing your balance. His legwork was pretty good tho.
The ultimate show-off move that's actually effective is back-flip into cartwheel, where you hit the other guy with both feet in the head. Smacks harder than a heavy-weight boxing champing even if you're a twig. Just gotta train to be a gymnast for about 10 years to pull it off.
Realistic street fighting advice is prioritize not getting hit and watch the other guys feet, if he lifts one foot off the ground just shove/pull him and he'll fall over.