[Dan Hibiki]

A note on Vegetto: Vegetto never goes Super Saiyajin 2. He only powers up to Super Saiyajin. My only guess is that Vegetto realized that he didn't need to go further, because it is evident in the Super Buu battle that Vegetto absolutely owned Super Buu.

On the note of the Room of Spirit and Time: you can only be in there for a total of 48 hours in your lifetime. Goku spent a bit in the room when he was a child, and spent less than a year the second time. My argument for this, though, is that Vegeta is told by Piccolo that he can't spend all that time in the RoSaT before the Cell Games or the door'd disappear. If it were a technicality that he had to come out and go back in, Piccolo would've told him.

Anybody with a good deal of evil in their heart absolutely gets owned by Akuma (or Shin Akuma, same guy, just giving a damn). Shun Goku Satsu! Free ticket to Hell. You also have to consider Akuma's invincible teleport. He could just teleport all over the place and nail them in the back with the Shun Goku Satsu.

I further think that Akuma is immortal in the sense that old age can't kill him. Look at Muten Roshi, the wrinkled and bald immortal showing his age, for instance... just 'cuz you're immortal doesn't mean you can't show your age at all. Also, the world of Street Fighter is one where sheer determination and training can let a person endure deep sea pressures and need no air for hours on end, and sink an island with a single powerful chop (both Akuma, see SFIII:3S Akuma ending and SFA2 official story respectively). I hardly think Akuma being immortal against natural death is a stretch in this case.

On Gill: yep, Gill can revive himself. "RESURRECTION!" he just gets up and poof! There's his health bar again! And also Gill could take out any DBZ fighter with his insanely powerful and all-reaching Seraphic Wing attack. There's no escaping it, you can block it, yes, but it is the power of a God on Earth... there's no denying Gill.