Brass balls and a titanium nutsack
I agree on the Cardio. I also think a sense of detachment, ala the Machida brothers is important as well.
Cardio overcomes a lot.
Wwe style shit talking ability 
When you look at dominant champions, these things always stand out...
Talent
Skill
Intelligence
Passion
Focus
Toughness
I think the top attributes are the ones that can't be taught; chin, power, natural athletic ability, mental toughness, smarts, kinesthetic learning ability etc. Nobody is born a black belt or champion but people are born with the things mentioned above 
A pink mohawk like Julian Lane
Huge weiner
Cardio
Ability not to panic
Magical powers