Galactus

Here are the basics:  Galactus began life as Galen, a badass Steve Austin / Buck Rogers space explorer on the planet Taa, where even though he was basically some average schmuck he had all kinds of awesome Flash Gordon adventures hauling ass around the universe trying to explore the galaxy and be fucking awesome for his people.  Well, one day Galen came across some massive radiation plague that was wiping out every planet in the galaxy, and, when he realized that this plague was actually the entire fucking universe collapsing into itself, Galen decided, fuck it, let's go out in a blaze of badass glory, load a bunch of assholes into a spaceship, and crash head-on into the fucking end of the universe like Jimmy Dean plowing the steering wheel of his Porsche 550 Spyder (too soon?  I can never tell...).

Well the universe has a funny way of rewarding people who completely lose their fucking minds and do badass shit just for the hell of it, and instead of being crushed into sub-atomic nonexistence by the compounding destruction of reality like the rest of the dumbasses who agreed to fly into their own deaths alongside him, Galen transcended into badass Nirvana, survived the Big Crunch of the Universe, and was encased in cryostasis in the Cosmic Egg that formed the catalyst of the Big Bang and created our current universe.  Galen, now fused with the physical embodiment of the metaphysical aspects of Eternity and Death (yes, both of them), exploded out into the new universe like a blackhead being popped off God's ass, hurtling through the cosmos in his apparently-indestructible starship. 

Galen's ship eventually fell into orbit around some random bullshit planet in some asshole region of the universe, and when that planet got all-out invaded by some other random, equally-assholic civilization , both sides were all like "what the fuck is up with this random alien spaceship" and fired pound-you-in-the-ass surface-to-space missiles at it.  The missiles hit the ship and woke up Galen, who, apparently bitter about not being able to sleep in for another couple millennia, transcended his own mortality, became a living god known as Galactus, and promptly exterminated the entire militaries of both sides WITH HIS MIND because he's fucking just completely insane like that.  Then, just to be an asshole, he ATE THE PLANET because seriously fuck that place.  Oh yeah, then he built a spaceship the size of an entire planetary star system and took off on a mission to visit new worlds and civilizations and basically eat everyone he could find because fuck it what the hell are they gonna do about it anyways.

Well, as you might guess, a reputation for woofing down planets like Daryl Hannah from Splash bodyslamming her face into Red Lobster's all-you-can-eat popcorn shrimp feast can earn a guy some pretty badass nicknames, and before long Galactus was known as the World Devourer, World-Eater, and other things that involve planets and eating and HOLY SHIT-

Ok whatever, let's say you're not into the cosmic shit and you aren't fully convinced by the FUCKING RADNESS of thte fact that Galactus randomly decided to turn a guy named Norrin Radd into a silver glowing dude who flies around the universe on a warp-drive-equipped surfboard, then used this so-called "Silver Surfer" to careen around the galaxy in the most bitchin' manner possible so he could warn  planets that they're about to get popped like a Xanax in the name of Galactus's unquenchable hunger for the life blood of all organic life in the universe.  Even if that were the case – and it's a stretch, my friends – let's still take a moment and attempt to rationally examine Galactus's power by theoretically pitting him against a rogue's gallery of popular superheroes.

Galactus vs. Wolverine:  Wolverine has adamantium claws and mutant healing factor.  Galactus EATS PLANETS.

Galactus vs. Superman:  Superman can fly, has x-ray vision, inexplicable cold breath, can crush coal into diamonds with his thighs, and once deflected a bullet with his face.  Galactus wields the Power Cosmic, can levitate, teleport anywhere in the universe at will, restructure his molecular makeup, project concussive energy with unmeasurable force anywhere in known space, is telepathic, can raise the dead, create solar systems, and create interdimensional portals whenever he wants.  He's also invulnerable, possesses godlike power, and can punch you so fast it breaks whatever the Sound Barrier equivalent is for the Speed of Light.

Galactus vs. Batman:  Batman is a regular guy with a bulletproof caped suit, sweet detective skills, a cool turbocharged Batmobile, and a seemingly-endless supply of titanium boomerangs shaped like his personal insignia.  Galactus travels the universe in a ship the size of our Solar System and derives his powers from forcibly ripping out the life essence of entire civilizations with his mind, then crushing their utterly-drained, comatose planets into asteroid dust WITH HIS GODDAMNED TEETH.

Galactus vs. Punisher:   The Punisher can dual-wield M249 SAW machine guns while simultaneously pulling an RPG trigger with his teeth and kicking a crocodile in the face with an explosive-arrow-tipped knife strapped to the heel of his boot.  Galactus died once when the combined military might of the ENTIRE UNIVERSE simultaneously nuked him with weapons of mass destruction, except that by "died" I mean he dispersed into cosmic energy only to be re-integrated at a later date and resume his inexorable quest to stomp out all life in existence with his unabashedly-purple man-boots.

Let's look at the track record.  He eats Kallreich the Unconquerable, a guy who by definition was unconquerable.  He eats the Throneworld of the Skrulls, a ruthless race of warlike assholes, just because he needs to prove a point about something.  When Dr. Doom usurped the Silver Surfer's powers and became Doctor Silver Surfer of Doom Galactus just banished him back to Latveria with a wave of his hand (this, by the way, is part of why I love Doctor Doom).  He fought Thor, Loki, most of the Norse gods, and crushed out the Elders of the Universe when they tried to overstep their bounds and tell Galactus that some guy who mysteriously ascended to godhood should stop dictating the order of the universe by devouring planets.  When some jackass created an alternate universe to house the Secret Wars, Galactus showed up and almost ate Battleworld – you know, the place where EVERY SUPERHERO EVER was fighting each other – but was eventually talked out of it and quit only because he decided it wasn't worth the effort (apathy ftw).  He surfs black holes.  He created the Silver Surfer, then dumped him and took on the Girl Human Torch as a sidekick.  He imbues people with the Power Cosmic on a whim, then takes it away without warning, and every time he's pissed he threatens to eat Earth until Reed Richards and the Fantastic Four do whatever random bullshit thing he wants them to do. 

Galactus's only weakness (if you can call it that) is that he starts to lose power when he hasn't eaten planets in a while, and every once in a while some asshole like Thanos gets a cheap shot in on him while he's weakened and almost kills him.  Well, one of the awesome things is that Galactus is such a hardcore planet-murdering bastard that when Reed Richards saved him from imminent death, an intergalactic tribunal was called to indict Richards for intergalactic war crimes simply for the transgression of showing mercy to this asshole.  That's pretty baller.  Richards defended Galactus for a while, but eventually Galactus was like FUCK THIS SHIT, showed up, took the stand in his own defense, and "you can't handle the truth"-ed everyone into realizing that he was a stabilizing force in the galaxy and that the people of the universe actually NEEDED to be forcibly shoved down his cosmic esophagus and slowly digested by his ridiculous planet-dissolving stomach acids.  Oh, then he wiped everyone's minds so that they were like what the hell just happened, leaving the tribunal with just the vague recollection that maybe they shouldn't fucking fuck with cosmic entities capable of ripping reality apart with their fists.

Even though Galactus was created as Jack Kirby's weird bizarro interpretation of a semi-sadistic purple-pope-hatted Judeo-Christian God, probably the best thing about him is that he's such an all-powerful entity that even though we see him in a blue jumpsuit, other civilizations across the galaxy perceive him differently.  The theory is that he's so omnipotent that alien cultures simply just view him as the most terrifying and awe-inspiring thing ever, and that's how he likes it. 

And yeah, that's pretty badass if you ask me.

Now where the FUCK is that cheeseburger.

Links:

http://marvel.com/universe/Galactus

http://www.comicvine.com/galactus/29-2149/

http://marvel.wikia.com/Galactus_%28Earth-616%29

http://en.wikipedia.org/wiki/Galactus

Special thanks to Matt Harding of Where the Hell is Matt? for his invaluable input