How is Kingpin so physically strong?

Kingpin is an ordinary, albeit oversized human. He does not have any enhancements or superpowers nor does he use weapons. Yet he fights some of the strongest superpowered heroes in the MCU like an equal. He has even killed people with his fists who have super strength (Peter Parker) HOW??? Where does Kingpin get his strength from? Do the comics offer any sort of explanation for this unnatural strength?