Who is the most powerful Marvel villain?

Thanos' most famous omnipotence was in the comics “Infinity Gauntlet”, which became the backbone of the Marvel Cinematic Universe. During the “Thanos Quest” miniseries, Thanos collected the six universe-controlling Infinity Gems (sometimes called the Soul Gems) and placed them together on a metal gauntlet, allowing him to simultaneously wield his power.

The MCU, of course, turned the Infinity Stones from a plot device into a multi-movie MacGuffin fetch quest, giving each individual stone and its powers far more importance. But the ending was the same: Thanos collected the six and wiped out half of all life, even if he did it for the sake of cosmic “balance” rather than trying to woo Death with a mass offering in her name.

But Victor Von Doom claimed to be godly in the pages of Marvel Comics when Thanos was just a glimmer in Mr. Starlin's mind's eye. One of the most famous scenes in Stan Lee and Jack Kirby's original Fantastic Four is #57-60. issue when he steals the Power Cosmic from the Silver Surfer and wreaks havoc.

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It was poorly adapted in the 2007 film Fantastic Four: Rise of the Silver Surfer. (“Let's all turn around!” Doom doesn't speak words!)

In Jim Shooter's original 1984 Secret Wars, the Marvel Universe's greatest heroes and villains are brought to Battleworld by a godlike being called the Beyonder who wants them to fight for his entertainment. Doom eventually steals the Beyonder's powers and becomes the main villain of the series. That story, right up to God Emperor Doom, is of course the basis of 2015's Secret Wars, even if the latter is a lot better.

Before the “Secret Wars” remake, Hickman also explored Doom's rise to godhood in “Fantastic Four.” In the epilogue of “FF” #16 (drawn by Steve Epting), Doom claims two The Infinity Gauntlets from the destroyed interdimensional “Council of Reeds” and instead creates a “Parliament of Law” made up of variants of himself.

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Fantastic Four #611 (by Hickman and Ryan Stegman) followed suit. While in the universe where the gauntlet first came from, Doom finds a void and fills it with creation, clearly referencing the Book of Genesis. However, Doom's creations bring him down. (“It was then, on the seventh day, that Doom realized a mistake had been made. He had created the universe in his own image.”) Doom ultimately needs the Fantastic Four to save him. and concludes that ruling as a god was “under (him)” anyway.