Is Boxing really the most powerful martial art?
Don't get me wrong, Karate has katas and horse stances and other stuff not practical in a street fight and aikido where you rely on your attackers momentum would not work on a great boxer. A great boxer would beat the tar out of most karate and thai chi and aikido and practitioners of most eastern martial arts. There might be a few exceptions like Bruce Lee but mostly I just see boxers beating the crap out of them. Capoira also loses to boxing, its a DANCE.
BUT... Other contact intensive martial arts like MMA, Muay Thai Kickboxing, and Brazillian Ju Jitsu are REALLY REALLY GOOD. I do not see any boxer except maybe Mike Tyson (and even then its not a guarantee) beating someone well trained in a combat art that includes wrestling/grappling ability, kicks (including knees) and strikes not allowed in boxing like elbows and head butts. As powerful as boxing is and against most people it would work just fine I think its limits would cause pretty much any boxer to lose to a more well rounded martial artist if the fight was a street fight and not a boxing match. I believe any of the members of the Gracie Ju Jitsu clan would beat this guy in a fight but lose horribly to him at just boxing.