Is Marciano the number 1 h2h Heavyweight?

No, top ten is arguable but extremely unlikely.

Number one is ridiculous.

 

To be pedantic he wouldn't necessarily have to beat ever other heavyweight to be #1.

But no he would not be top dog.

 

Not a chance

 

Nobody would have beaten every single heavyweight before or after them.

There is somebody who would have got better results vs every heavyweight before or after them, than any other heavyweight could have managed.

I think that what you are really asking, is was Rocky Marciano that man?

While we cannot rule the possibility out, I submit that it is unlikely.

His size, and style, both suggest that other men could have been more versatile, against a range of great heavyweights.

 

Let me go a little further.

Would he have beaten every single Heavyweight before or after him?

No he wouldn't BUT the more interesting question would be:
Can beat Marciano any Fighter in his own Weight Class? There was no Cruiserweight back then.

Marciano would DESTROYED anybody in todays Cruiserweight division.

 

No he wouldn't.

He'd probably beat them all. But destroy? Nah. He failed to destroy lesser men.

 

Will @Brockton Rock please stand up?

 

Marciano KO6

Vs who? Does it matter?

 

This. People love throwing around blanket statements like beating every heavyweight before him or after him. Every fighter has a style they struggle with and people need to remember just how many heavyweights came before and after Marciano.

 

Ali has the best chance.

 

Not a bad shout.

 

Being number 1 h2h doesn’t equate to not losing to a single HW before or after.

Ali is #1 h2h, no debate.