inn the movis have one man punch a knoc-out on a other guy, is that relly possibul

Watch boxing much?

I can think of 4 places on your face that will knock you out instantly. I can think of another 3 places you can punch to knock them out from the back. I'm not telling where to protect the kiddies who may be browsing the forum.

In hawaii a man was recently charged with murder after he walked up to a toursist and killed him with one punch to the head.

It's absolutely possible and quite common.
A knock out usually occurs from a head blow that is not seen coming.
I'm not a trained boxer but have dropped more than one man with a single punch on the chin.
Some actually out for several seconds and some stuggling for coherency.
It's not pretty but it does go with some lifestyles.