That's not easy. Offhand maybe Joe Louis barely gets five. Walcott II, Braddock, Baer (although Baer could have got up the ref did toll 10), Lewis and Conn. Sharkey and Schmeling were past their prime and Carnera was a TKO if memory serves me. So this is a rough one.
Might not fit the criteria but here is my list Maxie Rosenbloom Willie Pep Paulie Malignagginininin Joey Maxim Tommy Loughran Jimmy Young Chris Byrd Miguel Canto Harry Greb Julian Jackson Samart Payakaroon
Donaire is the only one. Darchinyan Arce Montiel Marquez Sydorenko Nishioka All went down from 1 punch. Yeah I know technically Montiel got up but the ref should of stopped it and he ended up stopping it few seconds later anyway. Nishioka got as well but his corner throw in the towel right after
Boxed Ears seems to always be sarcastic in his posts. The only time I see him be serious on Classic is when he praises Jimmy Young.