[@Moonman]: Hrm...

Well, sine he's the first "villain" I've seen roll in so far, I actually have to ask: what's his motivation for sticking along for the ride? Is it just to find stronger opponents, or what? Will he be actively picking fights with the characters? Like, if he's in a group with a strong martial artist, for example; will he be attempting to duel and/or take their lives often, or what?

Breaking an island in half... That's... Pretty absurd, I gotta say. To be fair, though, we've got Saber and her Excaliblast, but that doesn't have nearly as much power and can only be popped once every... While. So.

Shun Goku Satsu needs a very specific counter to go through, but given that it's Akuma's signature move, this creates a dilemma. I'd think that making it do super heavy damaged to major characters is okay, and let it keep the instakill tag on advanced mooks. Things like greater dragons and stuff, though, where lore generally states that their soul is much stronger than those of humans would have the former tag applied to them though.