You’ve got to include Joe Louis ‘The Brown Bomber’ Deontay Wilder ‘The Bronze Bomber’ Herol ‘Bomber’ Graham Mike ‘Dynamite’ Dokes Alexis Arguello ‘The Explosive Thin Man’ Rafael ‘Bazooka’ Limon
In the last 35-40 years, since I've been following, I'd say Julian Jackson & Deontay Wilder. Those were the two best one-punch knockout artists I can think of. I'd rate Jackson at the very top because he could do it with either hand. Hearns I suppose would be #3, maybe even #2 since he had a far tougher line-up of opponents than Wilder. Tough call. Prior to that, I'd add Jack Dempsey, Joe Louis, Bob Foster, Earnie Shavers, George Foreman, & Alexis Arguello
Deontay Wilder has yet to knock out anybody worth mentioning. Even with his so called "one punch knockouts" they were against lower level fighters who were walking toward him trying to punch.