Ippo is being overrated as hell here, Rocky took punches from Ivan Drago who punches strong as the bite of a silver back gorilla, in Rocky III he showed amazing speed, could smash the ribs of a robust bovine meat, that is amazingly strong, thick and dense bones, strong meat in there, is a superhuman feat to do that so easily when normal humans would probably break their hands in there.
Rocky knocked out Clubber Lang and Drago that were clearly superhuman in their primes, and could punch at strengths that could even harm some large animals, Drago could maybe even harm or kill a adult lion with that punches pretty easily, Clubber Lang was a rocking machine, he had bursts of power like a leopard.
Ippo is showed to do some fancy anime like feats, but they were all those laughable script stupidity for dramatic effect, and even if he used that Balboa would always get up specially if he was bloodlusted, and wouldn't stop hitting with brutality and skill until Ippo was out.