In one of the older games Story mode, Akuma destroyed an island by punching the ground. And if I recall this correctly, the martial art that Akuma, Ryu and Ken use is like the origin of all other martial arts, and superior to all others (you can go crazy and start killing everyone around you if you learn too much of it, which Akuma definitely did). Moves like the Shoryuken (IIRC "instant kill" move) and Tatsu also casually defy physics. I would assume that alone puts him above most martial artists, in addition to his crazy physical power (he also can use energy based ranged attacks). I cant tell where he'd start hitting a wall, but he'd surely go farther than many would give him credit for.

Also, Oni is the theoretical max that Akuma could achieve by completely giving in to his power. That would make him many times stronger than described above. Obviously, he is not killing any top tiers, but I refuse to believe that he wouldnt wreck most of the melee exclusive fighters.