not so much as a ripoff of ryu/ken and especially dan, since akuma was in the game before dan, anyway he was the only person to master the dark hadoken and he also has the same moves as ryu,cept alittle diffirent, and thats all i can remember since i just watched street fighter alpha the movie a couple of days ago so yeah...
and i think is one of strongest in the game, though i never play as him..