In one way obviously, and obviously the more fights you have the harder it is to stay unbeaten. Mayweather claims he's the best ever because he went undefeated. If someone wants to claim Marciano is the GOAT then their opinion is valid.
95% of the best ATG heavyweight champs could fight their best night after making the curent cruiser limit 24 hours earlier. 220lb is achievable.
Not impossible but improbable. If true the same must be said of johnson, schmeling, Dempsey, Tunney, Spinks, Patterson, Braddock, Charles, holyfeild, Moorer, Ellis. It’s not just Rocky. IMO the Rock was likely 190 odd in the ring anyway. I think he could make 179? But why bother?
That's only true up to a point. If many of those fights are against poor to average opposition, (or past prime fighters not at their best weights - seeing as it is a Marciano thread) it could be relatively easy to stay unbeaten. Being unbeaten is often more a testament to the matchmaker's skill as much as the fighter's.