While Galactus’ awesome cosmic power is unquestionable, he isn’t completely invulnerable to attack, including from dramatically less powerful beings like the Avengers. In fact, one surprising Avenger can actually beat Galactus, and Marvel Comics proves it.
Galactus is a cosmic entity who consumes entire planets in order to satiate his endless hunger–a being who is more of a force of universal nature than a man, though he didn’t start out that way. Galactus was originally called Galan of Taa, more or less a regular humanoid who lived in the universe that existed before the Marvel Universe fans know today. During a multiversal renewal cycle, Galan’s entire universe was broken down to nothing until it once more exploded with life at the dawn of the new universe. While everyone in his original existence died, Galan was filled with a new kind of power and was transformed into the god-like being Galactus–though his continued existence came with the terrible price of keeping this new universe in check by endlessly devouring planets with the full might of the immeasurable Power Cosmic at his disposal to keep him from ever being stopped.
In Cosmic Ghost Rider #2 by Donny Cates and Dylan Burnett, Cosmic Ghost Rider aka Frank Castle tracks down Galactus after he stole an infant Thanos from his crib in order to raise him as his own and keep Thanos from being a murderous tyrant. Ghost Rider wanted Galactus’ help since, in his original reality, they became friends after Cosmic Ghost Rider became his Herald. As Galactus refuses Castle’s request, Ghost Rider is attacked by Cable and a group of other superheroes from the future who traveled back in time to kill Thanos before he grows up into the villain Castle unintentionally raises him to be. In Cosmic Ghost Rider #3, Galactus brutally attacks the time-traveling hit squad, so Cable goes back to the future to grab a piece of tech that could defeat Galactus–tech developed by the Avenger, Ant-Man.
Using Ant-Man’s Pym Particles, Cable shrinks Galactus down to the size of an insect, places the World Devourer in the barrel of his gun, and shoots him into space. Cable admits that this was just a temporary measure and that Galactus will eventually be back to normal, but the fact that Hank Pym’s invention had that much of an effect on Galactus means he could very well be permanently defeated. Since the Pym Particles worked against Galactus, Ant-Man could conceivably develop an even more effective solution using an enhanced version of the same tech seen here in this issue. If Hank Pym could permanently shrink Galactus and use his proven scientific brilliance to trap him in a containment vessel or even the Microverse, Galactus would effectively be eliminated and his reign of cosmic terror would come to a swift and microscopic end.
As it stands, however, Ant-Man can seemingly only defeat Galactus for a short amount of time. While that alone is an impressive feat of cosmic proportions, it only scratches the surface of what Pym could do as it proves Galactus is vulnerable to that particular method of attack. Even though Galactus is the truest example of cosmic horror in Marvel lore with enough power to defeat practically anyone who gets in the way of his next planetary meal, Marvel proved that Galactus can actually be beaten by one surprising Avenger.