Rickson Gracie because he has 400+ wins and never a loss
"Rickson has at least one loss — from the 1993 U.S. Sambo Championships in Norman, Oklahoma, where he was defeated by American Ron Tripp by Total Victory via uchi-mata in 45 seconds. Rickson disputed this loss, claiming he was misinformed of the rules of the event.[8][9]"
"Hélio Gracie disputed Rickson's claim to have had over 400 fights. According to Hélio, Rickson has only competed in fights that are commonly known and reported: the two against Rei Zulu and those that took place in Japan. Hélio alleged that Rickson uses practice and amateur bouts to obtain a number over 400, and that if he counted his fights like Rickson does, he would have in excess of one million.[12]"