I think 1985-1989 Mike Tyson would wipe the floor with every heavyweight that came after that period of time.
There have been better heavyweight boxers than Tyson, but there’s a case to be made that nobody who has ever fought at heavyweight would beat 1980s Tyson. He was 20 year’s old and had hard experienced heavyweights shitting themselves just seeing him walking into the ring. He was a fucking animal!
Tyson lost his edge and a bit of fear factor in the 90s, but even 90s Tyson would still beat every heavyweight around today.