Let's go with the tvtropes Five Bad Band then...http://tvtropes.org/pmwiki/pmwiki.php/Main/FiveBadBand
Big Bad: The Master (Doctor Who)
Why?: The Master's a planner, the one who can manipulate people and set multi-layered plans into motion just as well as The Doctor himself. Manipulating a group of villains would be child's play, and having them protect him would make him unstoppable.
The Dragon: Darth Vader (Star Wars)
Why?: Not only is Darth Vader the ultimate second-in-command in Star Wars, he's also the page image for The Dragon (http://tvtropes.org/pmwiki/pmwiki.php/Main/TheDragon). Powerful, ruthless, intimidating, and fiercely loyal (unless you slowly torture his son in front of him), Vader would be the nightmare no hero could stand against.
The Evil Genius: Dr. Doom (Marvel Comics)
Why?: Doom is smart. His intellect is almost the same as Reed Richards, who's capable of bending space and time so he can fit more food in the fridge. Dr. Doom challenges the entire Marvel Universe on a daily basis, outwitted a GOD to steal his power in Secret Wars, and took over the world TWICE (as well as in countless other What If? tie-ins.)
The Brute: Doomsday (DC Comics)
Why?: The Brute is big and dumb. Doomsday is brute force incarnate, becoming so popular, he has his own trope (http://tvtropes.org/pmwiki/pmwiki.php/Main/GenericDoomsdayVillain). He doesn't care for morals, politics, values, plans, strategy...all he does is charge into a situation and murder everyone in a 5 mile radius. Oh, and he also killed Superman.
The Dark Chick: Kefka (Final Fantasy VI)
Why?: Although he's male, Kefka is still a "a giggling, unserious, destruction-loving maniac." While the other villains are brooding, Kefka would be laughing maniacally while staring at you with his crazed eyes and changing the pitch of his voice to spine-shivering frequencies. He's so crazy, he destroyed THE WORLD for GIGGLES. Also, I can't stop thinking about him and John Simm's The Master being in the same room.
There you have it.