I am a martial artist, thus I can punch hard. I am also a weightlifter-powerlifter, so I am large, muscular and strong, and I can use my weight and strength well in strikes. Once my 6'-4", 250 lbs. pal Bill Jones challenged me to a contest in breaking concrete. He is a black belt in Okinawan Isshun Ryu Karate. He stacked six pieces and used a Shuto (Chop with the side of the hand) that had his hand move about a yard. He split the top three pieces. I then stacked six more pieces and placed my fingertips against the top piece. By closing my fist, I shattered all six pieces, so my 3" Seiken (Fist Punch) was much more powerful than his 3' Shuto (Chop). I fear that I would kill Mark Zuckerberg if I punched or chopped him with my full force.