How many match ups can you think of between two elite fighters who have had in excess of 40 fights (obviously over 60 for Clen), both fought a bare minimum of 20 + world title fights, have been pros for 16-17 years, and neither have ever been down? Surely that's got to be pretty rare?
Bivol?? Half his opponents took his shots. Sullivan is the only relevant opponent he's stopped and that was in the dead of the 12th round.
You can argue that Lamotta has a better chin than GGG. The St. Valentine's Day Massacre is a shining case for that.
Not even the best of my lifetime, by my estimation (granted, the second of these examples took place at 168 after Chris had moved up); Though it might've been Gerald ultimately took a punch too well for his own good, you don't eat multiple clean hits off Jackson and stay vertical/compos mentis if your beard isn't absolute granite.