That big bald guy in that bar scene is Frank Degeberg from the Degeberg Academy in Chicago. He's a real character and cross-trained in a number of different martial arts. He would be hard for Segal to beat in a real bar fight.
Another notable martial artist that Segal faced in another one of his bar fight scenes was Dan Inosanto, 'sticks'. I'd put him in the unbeatable category for Segal, or almost anyone else in the world in a real 'stick fight'.
I didn't know about those two fighters you mention. Seagal hasn't been tested in a full contact ring, with rules, or a bar fight with the best bar fighters. We only know that he's good, not that he's the best.