What would happen if you punched Superman in the balls? His testicles would swing back and hit you with the force of a wrecking ball, suspended from a 20.0m cable and with acceleration up to 10.0m per second. Don't EVER do that! Superman getting pissed off, its very powerful shit, precisely because he doesn't do it often.
Now, imagine pissed off Superman punched you in the face. If his fist has an average mass of 300g and its moving 99% the speed of light, he would have a total energy of about 190,000,000,000,000,000 (QUADRILLION) joules. That's 45 megatons of TNT. That's over 2,800 times more powerful than a nuclear bomb dropped on Hiroshima. The temperature of his punch would be 143,999,999,999,540.3 degrees fahrenheit, which is 5 million hotter than a core of our sun!!!
For more crazy shit and other stats about the power of Superman's punch I suggest you WATCH the video bellow. And yea, keep in mind the balls story.
video story interpreting by Jake Roper