Capcom likes to go nuts for the bosses of the Versus series games, but they all share a common thread: any skills or strategy you've employed on the path to the final fight suddenly become useless. You know how you've been learning to combat super-powered tag teams up until now? Here's a gigantic, solitary boss who can obliterate your team in seconds. Have fun! Oh, and if your team doesn't include someone with copious projectile-spamming capabilities, just give up now.
Galactus, the cosmic, planet-eating entity from Marvel lore, is like a Greatest Hits of the unfair tactics used by his Capcom-designed predecessors. He's got the imposing size of X-Men vs Street Fighter's Apocalypse, the non-stop laser beam barrage of Marvel vs Capcom's Onslaught, and the unflinching, massively confusing attack animations of MvC2's Abyss. Every time Galactus claps his hands, one of your teammates dies--literally. And as if this fight wasn't hard enough already, Galactus makes you fight two metallic puppets for his amusement before you can even take a crack at him. After you lose for the tenth time, you won't even care that Galactus is destroying Earth because of your failure.