Wow...
Akuma's greatest feat was cracking a mountain down the middle...with his STRONGEST technique.
About how many comic characters can do that? And how many wouldn't even have to use their full strength? Exactly.
Akuma's only chance against most upper tier comic chars is his raging demon--it literally sends he and his opponent to hell, where their souls are attacked by demons. Only if you completely empty your mind/body/spirit will you survive the attack.
Then again...his RD is pretty slow so chars with super speed could avoid it and ask "why is he sliding forward like that?." Then they would beat him down.
Akuma should only be pitted against "street level" comic chars--and he can't even beat some of them.