Secret Rings casually giving Sonic his best non-Super form for this.
What with the crazy shenanigans Erazor Djinn could do with four - Darkspine Sonic had three - which included wiping clean and (almost, had Sonic not intervened, Erazor would have) rewriting the Arabian Nights universe, even Cosmo, Wanda and SpongeBob can do very little without Breaking Da Rules - !reference! - or acting out of character.
Darkspine as a transformation is very underestimated. If not for the stat advantage in favour of the latter, it'd be up there with Super Sonic.