And that Dante was no where near as powerful as DMC2 Dante. Oh and umm...show me where the creators said he had all these powers in AC because last I checked...speculating what he can shows the fanboyism in you. Sephiroth is no where near as fast as normal Sonic.
Its not speculation, that Sephiroth is the most powerful Sephiroth according to the games creators, meaning he has all the powers of previous Sephiroth's, especially considering all of them but Supernova are Sephiroth's innate abilities that he's always had. He doesn't use them, because as I've explained multiple times, he isn't trying in that fight, he wants to keep Cloud alive and taunt him.
Sephiroth doesn't even come close to reaching the speed of sound. And please Fusion Samus is a different debate all together. Fusion Samus is far superior then Prime Samus.
Are you kidding? Sephiroth can move a hell of a lot faster than the speed of sound. He can move faster than light(teleportation), which we all know is faster than sound. And Cloud is far superior to Samus prime as well, but Sephiroth is still far stronger.