The Ultimate Nullifier, the Repulsor Tech Node, and Cerebro are all examples of the most powerful technology of Marvel Comics. And being technology from Marvel Comics isn't where the similarities between these devices stop. While these devices are all best known for helping to save the Marvel Universe, they also all feature the capabilities to wipe it out (or, at the very least, wipe out large chunks of it).
Just like in real life, much of the technological advances made in the Marvel Universe can double as militaristic weaponry. Sure, the Repulsor Tech Node creates clean energy, but it also can function as a powerful detonation device. Cerebro helps to locate mutants, but it can also be used to terminate them. So, it's basically impossible to talk about the most powerful technology in the Marvel Universe without really talking about the most powerful weapons of the Marvel Universe. The only difference between the two is the person wielding them.
The Ultimate Nullifier
What Is It?: The Ultimate Nullifier is a small, nondescript handheld device with the power to take out entire universes.
Who Made It?: The origins of the Ultimate Nullifier are unknown to mankind. The existence of the Nullifier was known only to immortals like the Watcher and Galactus. Humans only came across the Nullifier thanks to the Watcher breaking his oath to not interfere and showing the Human Torch where to find it across the universe. Johnny Storm found the Ultimate Nullifier at the home of Galactus.
How Could It Break The Universe?: The Ultimate Nullifier was first introduced to Marvel readers as a means for the Fantastic Four to eliminate Galactus. The Watcher was present for the FF's initial engagement with Galactus, and he warned them of the danger of using the Nullifier. The Watcher told Marvel's first family that they mustn't "turn the lever to full power. It could erase the entire solar system in one minute!" Galactus may have possessed the power to devour a world, but the very sight of the Ultimate Nullifier made him decide against conquering Earth.Powerful technology?
Kang The Conqueror's Battle Armor
What Is It?: Kang's armor is a high-tech suit filled with gadgets from the future.
Who Made It?: Nathaniel Richards, AKA the man who would become Kang the Conqueror, was born in an alternate version of the 30th century. He eventually discovered a time-travel device, traveled back to ancient Egypt, happened to meet the Fantastic Four, and became obsessed with conquering the heroes of Earth. To achieve all of his conquering desires, Richards constructed a suit of high-tech armor for himself.
How Could It Break The Universe?: Kang's armor, created with materials from the 40th century that respond to his thoughts, gives him a number of typical powers (like super-strength and -durability). But there are three main capabilities that make it universe-breaking. The armor is equipped with an antimatter shield (that can vaporize any Earthly matter who touches it instantly), time-travel capabilities, and an anti-gravity ray. Honestly, it's astounding Kang hasn't been able to use those abilities to ultimately end the Avengers (and life on Earth in general) yet.Powerful technology?
What Is It?: The Master Mold is an artificially intelligent robot through which all Sentinels are created.
Who Made It?: Bolivar Trask created the Master Mold to control and ultimately wipe out the Mutant population. Trask was a member of a government think tank entrusted with eliminating super-threats of any kind. Although he was tasked with keeping the world safe from all threats, Trask was particularly fearful of mutants and believed they would one day replace humans as the dominant species.
How Could It Break The Universe?: The Master Mold and his army of Sentinels fall into the same scary camp as all of the powerful militaristic AIs. The Master Mold was created by mankind to control the mutants, but quickly, the Master Mold decided he should be in charge of both humans and mutants. Over the years, Master Mold has proven himself to be hard to eliminate. He has continuously returned to fight the X-Men, and at one time, even managed to create a deadly virus that threatened to wipe out all life on Earth. There are multiple alternate futures, like the one shown in Days of Future Past, that show the Sentinels and the Master Mold having taken over the world.Powerful technology?
What Is It?: Cerebro enhances the telepathic abilities of its user to locate and identify mutants across the world.
Who Made It?: Charles Xavier created Cerebro as the ultimate recruitment tool for his school of gifted youngsters.
How Could It Break The Universe?: Cerebro enhances the abilities of the telepaths who use it. When a powerful telepath hooks up to the device, Cerebro greatly enhances their abilities to a degree most people wouldn't be comfortable with. For instance, Xavier once used the device to probe the minds of every single human on Earth, and Emma Frost once attempted to use Cerebro to wipe out humankind. In recent years, Xavier had Forge upgrade Cerebro for him. Now, Xavier constantly wears the device, and not only does it enhance his powers, but it collects an up-to-date backup of the minds of every mutant on Krakoa.Powerful technology?