I'd say stamina. Zab Judah has the speed of champions, but after a few rounds he blows his wad and gets dominated. Though no one attribute is the key to success.
I look at it as if two fighters had similiar attributes with a bit of stamina, heart, chin, power, etc and you have the guy that has the faster hand speed and he usually outclasses the other guy. Speed is the difference maker.
He also has the intelligence and mental maturity and fortitude of a 10 year old. That, more than anything else, has kept him from becoming what he could've become and not his lack of stamina. When a fighter gives up mentally, he also gives up physically. Judah gets easily discouraged.
Wrong ! What keeps those guys from losing is dedication & phenomenal preperation. What do both guys have in abundance beside speed.... STAMINA. Its because they push it to the limit in preperation for every fight, speed & power dont mean **** anyway unless you have technique & accuracy nailed, maybe vs C level comp but not at championship level, believe that ****.
Stamina easily. You can bang all you like for 6 rounds, or have great speed during this time, but if you have no stamina as soon as you meet a guy that is experienced and can take you late in the fight you are ****ed.
Exactly, if you take three fighters at the same level... you give one a 10% increase in speed, one a 10% increase in power and one a 10% increase in stamina - who do you think will win? Speed kills.
There was no stipulation that any of these attributes would be the only one on display. It wouldn't really matter if that was the case, the fighter would be useless. The point is, speed or power deteriorate through a fight if you have poor stamina.