Zulu was supposed to be unbeatable but Rickson beat him down and it shot him to superstardom in the martial arts world. They say that there was only 1 Gracie that could submit him when he was 17 but he unfortunately died years ago. He was said to be the best of any Gracie in any generation.
I always wanted to see Rickson tear Wallid Ismael apart. Wallid was the Gracies prize student if i remember correctly (
) and beat Ralph, Renzo and then Royce. Royce had just had a bad car crash and almost broke his neck, but took the fight anyway. He was subsequently choked out - his first ever loss in BJJ - but he opted to be choked out as opposed to tap out. A fully fit royce would have soundly beaten him. A fully fit Rickson would have destroyed, and then retired him IMO