What heavyweight has the best stamina?

Frazier had incredible stamina to do what he did with so much constant upper body movement. Rocky had great stamina obviously.

Ali had great stamina and an amazing ability to absorb body shots. Taking body shots are supposed to weaken you. Look at how strong he finished in the intense heat of Manila after taking a drumming to the body.

 

There’s a few candidates but I’d say Jack Johnson

 

I agree that Johnson is in the mix. Still upheld the fuel in his tank going almost 26 rounds vs Willard when he was 37 yo and out of shape.

 

Chris Byrd
Larry Holmes
James Toney

I don't include Jeffries because the level of opponent and the pace at which they fought at makes 20 of his rounds equal 4 modern rounds.