You can use any combination of three Marvel Heroes or Villains to defeat Galactus. Which characters would you use, and how would you use them? Would it even be possible?
You can NOT use Thanos; that would be too easy...even without the Infinity Gauntlet, he irritates the Hell out of the Big G.
I guess you can use DC heroes as well, but Galactus would probably just roll his eyes at them ~ I kid, I kid
(I wouldn't object to his making Hawkgirl or Wonder Woman into a Herald, though).
I guess if four characters are necessary, so be it.. but four is the maximum you can use.