Today's "Who Would Win?": The Powerpuff Girls vs. Buffy the Vampire Slayer.
Heroes: Buffy vs. Blossom, Bubbles, and Buttercup
I think it's safe to say that the Powerpuff Girls have the upper hand in this fight. Buffy relies chiefly on hand-to-hand combat; the Powerpuff Girls can fly and shoot lasers out of their eyes. It would be like a medieval knight vs. a fighter jet. We've never seen Buffy fight anything that flies. It's clearly not something she's prepared for, and even if she were prepared for it, she'd still be at a severe disadvantage. Besides that, three against one is still pretty unfair.
Winner: Blossom, Bubbles, and Buttercup.
Mentors: Rupert Giles vs. Professor Utonium
There was that one episode where Professor Utonium built a power suit to fight in. He never used it again, though, so I'm going to go ahead and say that doesn't count. In a fistfight, it wouldn't really be a contest--Giles wins. He's had years of combat training and he should be able to defend himself very capably. If you give Professor Utonium more time to prepare, however, there's a good chance he'd be able to cook up a spicy gadget as a trump card. So it depends who wins the initiative roll, so to speak.
Villains: Mojo Jojo, Him, Princess, Fuzzy Lumpkins, The Gangreen Gang, The Amoeba Boys, Sedusa, and The Rowdyruff Boys vs. The Master, Spike, Mayor Wilkins, Adam, Glory, and The First.
This is going to have to be a brawl. Who comes out on top? Well, with this many players, perhaps it's difficult to say. However, the Buffy side definitely has some heavyweights. The Mayor doesn't hit all that hard, but he is invincible. Glory is a full-blown god--that's going to be tough to deal with. The PPG side has Him as an incarnation of pure evil who messes with the good guys' heads but rarely does any physical fighting, but that's more or less matched point-for-point by The First, an incarnation of pure evil who messes with the good guys' heads but rarely does any physical fighting. If they cancel each other out, the only real threat on the PPG side is Mojo Jojo, and he's probably outmatched just in sheer power.
I expect both teams to turn on one another and tear each other apart with infighting. Come on, these villains aren't going to work together! So here's how it turns out:
Him sits for hours in a psychological-warfare stalemate with The First. Spike says "Bugger this" and walks away. Mayor Wilkins dominates the fight at first by being invincible, until the Rowdyruff Boys manage to tie him up and pound him into the ground and spend the rest of the fight tickling him and dumping buckets of sewage on him and so on. Glory, Adam, and The Master easily defeat Sedusa, Fuzzy, the Gangreen Gang, and Princess, but ignore the Amoeba Boys because they're pathetic, but Mojo Jojo storms off in frustration as he fumes and rants about how moronic the rest of his team is. Then in a freak accident, the Amoeba Boys somehow manage to unintentionally defeat all the remaining villains singlehandedly because they're stupidly lucky like that. Finally, Spike and Mojo Jojo run into one another as they're making their exits and go down to the local bar to get drunk. Then they team up to try and take over Townsville, but pass out in an alley instead.
Winner: The Amoeba Boys.