This is not a post that tells you the secret to winning fights to just walk away(Although you can do that too), but this is a certain punched I figured out on accident when I got into a scramble. Lets get into it so I don't waste your time.
Ready?
You going to do one thing only to increase the pain a person feels when you punch. And that is....
Just turn your knuckle up.
That's it.
If you raise you're middle finger up slightly while you're in a fist.... the middle knuckle should be showing the pointy end and it should stick out.
Compared to a normal punch the punch hurts extremely worse compared to the regular punch. Not because of the force behind it but, the sharp pain the comes from getting stabbed by your knuckle.
Try it for yourself. Unless you're fighting a complete grappeller or a supremely oversized man you should win because you will diminish his confidence. You can even though body shots with this. I made my cuz quit from hitting him right in the kidney with this. And the best part is if they brace for it....it hurts worse.