A Supreme Fighter.
Before this battle, Daneel had asked himself what one who was worthy of holding this title should be able to do.
Was it a Fighter who was able to win all battles?
At least in the Legacy Battle, that was impossible as no Fighter would be able to predict all the variables that he might have to face.
Was it one who would be revered and worshipped by all as the goal to reach?
Such a Fighter would still be crushed if he had to go up against a group of Fighters, or if he faced a freak like Daneel's elder brother who had already crossed most of the boundaries of common sense.
No, in Daneel's view, a Supreme Fighter was one who would be able to adapt to any situation thrown at him in order to accomplish what he wished, even if the World, itself, wanted him to fail.
A Supreme Fighter was one who would be able to take any situation and turn it into one that was favorable to him.