Introduced in the 2012-2014 run of Thor, Gorr the God Butcher is one of Thor's deadliest foes, easily slaughtering gods across the universe and nearly killing a young Thor in 839 A.D. The God of Thunder has been traumatized by this encounter, so it strikes fear in him centuries later when he sees Gorr's handy work once more, and his fears are justifiable when Gorr reveals his ultimate weapon.
After watching his loved ones perish while blindly praying to gods who never listened, Gorr makes it his life mission to liberate mortals from false deities, which includes every god in the Marvel universe. While he manages to do a brutal, thorough job with the All-Black Necrosword at his side, Gorr knows he needs to think bigger in order to accomplish his destiny. This is where his most deadly weapon, the Godbomb, comes into play, which is meant to wipe out all gods across space and time in one fell swoop.
The development of this weapon of mass destruction is as horrific as its intent. It all started when Gorr forced Shadrak of the Diamond Moons of Oghogho to watch as he butchered the rest of Shadrak's pantheon. While for most of this arc Shadrak lies about what he is the god of, he finally admits he is the God of Bombs. This explains why Gorr, who isn't one for pity, temporarily spares Shadrak, who was forced to design the Godbomb.
With this plan at hand, Gorr proceeds to go to Chronux, the Palace of Infinity, to murder every time god there aside from one. With the assistance of the last god of Chronux as well as the sacrificed gods' blood, Gorr plunges into the Pools of Forever to steal the heart of an Elder God, which would be the core of his bomb. The Time God is then forced to reprogram the pool so Gorr can travel into the future and pull Gods from across time and space.
While Gorr is focused on killing the gods, those he pulls through the Pools of Forever are not met with death instantly. Instead, Gorr enslaves them, forcing the gods to build the weapon that will lead to the extinction of their kind. This prolonged torture not only emphasizes how much Gorr hates the gods, but it also shows how dangerous a foe Gorr is because he is able to subject the most powerful beings of the universe. This is not to say Gorr doesn't kill the defiant gods under his watch, often time crucifying them.
When Gorr finally pulls a young Thor into his new world, he assigns him to the summit, ensuring that Thor will be the one to finish the Godbomb and be front and center when it detonates. Thor is new to this work, and he sticks out like a sore thumb because he continues to believe he is in a position to defy Gorr; however, the other gods have learned to stay in line otherwise they risk losing their lives too soon. In the eyes of these gods, after 900 years of torture and forced labor, they are no longer gods; they're slaves.
Despite their subjugation, these gods haven't lost faith entirely. After centuries of mining the cores of dead stars and destroyed planets to build the Godbomb, they have managed to save pieces of unstable matter to make a bomb of their own; however, their bomb fails to do any significant damage, proving once again how dangerous Gorr and his bomb are.
After a roaring battle between three Thors from across time and the God Butcher, even the Gods of Thunder fail to best Gorr and his weapon. The youngest Thor, as a result, is dragged to the bomb to be sacrificed. Along with the blood of the Time Gods powering the Pools of Forever, they also are infused in the Godbomb, and a few more drops of god blood is all that is needed to finish its construction.
Even when young Thor breaks free, Gorr, uses the heart of a lesser known god to trigger his masterpiece. As a result, Gods from every corner of time and space start to die, and the process is long and painful, with black bile suffocating them and their flesh falling off. However, Thor from the modern day refuses to let Gorr win, so he absorbs the force of the bomb while wielding two Mjolnirs in the heart of the weapon, which spares all gods.
The Godbomb is one of deadliest weapons against the deities of Marvel, and with Gorr wielding it, it is even more dangerous; however, there is one fatal flaw in its design. Neither Gorr nor Shadrak anticipated a god who would follow through with his godly duties. While Gorr believes gods promote false hope, Thor answers the prayers of his believers. In this case, it's the prayers of the dying gods he makes good on, destroying the bomb in the process.