[Ninjinister]

Spoiler:

I spent almost an hour on the last level because of Mono. That guy just ticks me off. Fortunately I found out that if you're doing a team attack at the exact time he does the detonation hammer, it won't affect you (though you risk most likely getting a failed team attack).

The GBA version has a much more diverse cast of bosses:
-Hun
-Karai
-Jersey Devil
-Machine holding Leo captive
-Max Winters
-Sea Monster (although you don't actually fight it, just feed it fish while fighting Purple Dragons)
-General Aquila, who summons the other Generals as special attacks

As for Mirage villains, I don't think the Purple Dragons are in the movie, are they? If not, I'd count them in that bracket.