As far as I can remember, at least by difficulty levels...
-Elec Man
-Quick Man
-Aqua Man
-Bright Man
-Slash Man
...That's all I remember from the top of my head.
Did you just do it because of Roahmmythril, or is it coincidence.
Anyways time for my least fav list.
MM1: Iceman. No revenge strategy, also bad footholders, BAD!
MM2: Heatman. I NEED, AIRMAN!!
MM3: Needle Man. Hard to hit with his weakness, hits hard, etc.
MM4: Toadman. not the boss, but just the stage mostly that Escargoo. If we are talking about the boss itself I vote Bright Man.
MM5: Actually did not play it.
MM6: Knight Man. Nice stage, but hard boss imo.
MM7: Slash Man. Dinos, HOP N SLASH MAN IS DEVIL.
MM8: I played the FC, and I need to say uh, had trouble with tengu man. No flinch and no voice telegraphs is hard.
MM9: Plug Man. No. Not the blocks. NOT THE BLOCKS!
MM10: Chill Man, I always have trouble with the buger.
MMV: Never played.
MMB (1 & 2): Never played.
MMK: Never played their games. Sorry. But in MM10 I would say enker. Gave me TOO MUCH TROUBLE SINCE I DIDNT HAVE B.CRACKER
(FAN GAMES INCOMIN)
RF: Charade Man. NOOOOOOOO!
Unlimited: Yoku Man. Do I need to say it?
Eternal: Clamp Man.
That's all for now...