[Fish Sandwich]

Yeah, Gaim was really one of the great lieutenant baddies in all of tokusatsu. The concept of this guy who's been manipulated from a young age to believe he's the hero, acting according to the whims of the main villain to defeat what he perceives as a bigger threat, only to find out too late he's on the wrong path, and simply succumb to evil in the end, now that's he's in too deep, and sacrificed too many people, it's a great arc. Those were the kind of hard-hitting moral dilemmas you only got from a show as daring and clever as Gaim.

But then, we're talking about what villains are most powerful, and Kouta couldn't even beat fate.

Man, I haven't dunked on Gaim that hard in a while.

Uh, more seriously, I'm changing my pick to Oma Zi-O until further notice. I just remembered that logically, he already has the powers of any other tough Rider you can name, including Odin, Evol, and whoever else, and I'm not sure we ever actually saw the ceiling on his powers in the series. I get the impression he could basically wave his hand and make it so you never existed to begin with, and he only refuses to do that because it'd get rid of his entertainment.