We should make this scientific: include every fighter who we can confirm has never been knocked out or seriously hurt and has taken clean punches by world class fighters. Then compare the power of the punchers they had to withstand. A fighter who's walked through the punches of several B level punchers often has the reputation of being strong-chinned, but we can't get a read on a fighter till he's been in with a puncher like Tito/Golovkin/Matthysse, whether he stays on his feet from their best shots or not.