When going over ko records of the sport's top punchers it seems the very best had many 1st round kos, I know some this is due to the level of competition etc but still consider the following: Jack Dempsey-27 Earnie Shavers-23 Gerald McClellan-20 Ray Robinson-20 Roberto Duran-21 Max Baer-15 George Foreman-15 Bob Fitzsimmons-16 Edwin Valero-19 Alexis Arguello-14 Tommy Morrison-18 Cleveland Williams-18 Sam Langford-16 Rocky Marciano-11 Julian Jackson-13 Thomas Hearns-10 Mike Tyson-22 Then we have great fighters not known for having big KO power many of these of course have very few first round kos- Evander Holyfield-2 Muhammad Ali-2 Jack Johnson-3 Jake LaMotta-2 Carmen Basilio-3 But then some big punchers had very few- Ron Lyle-0 Wilfredo Gomez-4 Carlos Zarate-2 Factors such as opponents, style etc fall into the equation but still first round kos are a very good predictor of punching power.
So many variables. Some guys like to warm up to the task, like to "download" their opponents' tendencies. Some fighters had more backing and had very curated careers, soft touches to boost their records. Others were just thrown to the wolves.
