Fighter with the best stamina

Mayweather Jr

He never gets tired.

 

Nonito Donaire for me.

 

Did. He never tired.

He just didn't look like his usual self. Age is taking it's toll.

 

Daniel Geale.

 

Carl The Cobra Froch

Legendary stamina and durability

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He did not.

There was no panting or any excessive breathing at any point in the fight.

He was still fresh as a daisy even at rd12

 

It's an impossible thing to judge because intensity obviously alters it. You can fight without throwing powerful punches and go for 100 rounds or you can fight balls to the wall and be out on your feet after 5 rounds. For example David Haye, people say he has poor stamina but he throws such powerful punches in combinations for a big man. He could fight at a slow pace and put less on his shots like an old timer and people would say he has great stamina.

 

I'm gonna go with a less obvious choice...Sergio.

 

A good example of volume over power. So is his stamina really that good if he's performing less work on every punch?

 

Sergio, froch, donire, pacman, mayweather, Guerrero, Ortiz, And others

 

Donaire has the athleticism to pick his shots and he is big for his weight class, Rios is also very big for his weight class so he might not be strictly throwing 'power' shots, just shots with good technique and his size does the rest.
I thought De La Hoya always fought at a reasonable intensity, even when he's not punching he was always tense so he was increasing his energy cost even when not punching, same thing with Cotto who would also get tired in the later rounds. The inverse of that was Roy Jones, very loose so he threw power punches and recovered well after every combination. I think there are a lot of factors with 'stamina', there is nothing objective about it unless two guys are throwing the same punches with the same relative intensity over the whole bout. That's why a lot of scientific tests regarding endurance are performed on a cycle ergometer, everything can be quantified. There is absolutely no way to do that when watching something like boxing as there are so many factors and individual styles/attributes involved.