Based on Ant-Man and the Wasp: Quantumania alone, it certainly seems as though He Who Remains was the more powerful and capable variant, having succeeded where the exiled Kang epically failed.
Galactus would win. Why? Because he is way more powerful than Kang lmao, Kang's only option is to get unimaginably powerful technology that can at least match Galan, somehow make him not be able to feed, or simply get an army or another powerful entity from another time/universe.
Who will be the next big villain after Kang the Conqueror?
2 Doctor Doom is the Most Obvious Choice to Replace Kang
With the Fantastic Four ready to join the MCU, Doctor Doom is sure to join them. He has spent his entire life struggling against Mr. Fantastic. If Reed Richards is to enter the MCU, Doom must preempt him.
On Earth-18854, Kang took the power of Galactus himself and became “Kang the Time Eater.” Because of his control of time, he may even be more powerful than the Celestials themselves.
Kang is stronger then Galactus! Kang is a threat for the entire multiverse (so also What If...?, Raimi and Webb trilogies, Fox X-Men Universe), has millions of Variants + the entire TVA can travel through the multiverse and through time!
History. Dormammu allied himself with Baron Mordo, Abomination, Cobra and staged an attack against their former master Kang the Conqueror, several years after Kang had conquered the world. Kang found himself unable to defeat Dormammu and fled back to prevent the formation of this reality.
However, Doom's power and the world he created were only temporary -as was Thanos' death- and not part of Doom's typical power-set. However, it does seem as though Thanos is still the victor considering all that can be done while wielding the Infinity Stones.
Marvel may recast Kang amid doubts about his viability as a villain, and Galactus would be a formidable alternative for MCU Phase 6. Galactus is a massive and well-known Marvel villain, with potential to be a recurring threat unlike Kang, ensuring a greater impact.
While Kang might have been a compelling villain in Loki, he does not need to appear again. Jonathan Majors ensured that he would no longer have a place in the MCU, and his character could join him as a piece of Marvel's history. Kang's story ended, and Marvel could never turn him into a satisfying villain.
In his last opportunity to escape, he had a brutal duel against Ant-Man, which resulted in Kang being shrunken and decimated by his own Engine Core, though his death inadvertently alerted the Council of Kangs about people interacting with the Multiverse, prompting them to take their own measures.
Eventually, Captain America defeats Kang before Ravonna uses his time crystal to regress him to an infant. In the post-credits, an elderly Kang joins Ravonna, Cosmo the Spacedog, Man-Thing, and the Supreme Intelligence in warning Captain America, Captain Marvel, and Iron Man of a new threat.
He also ensures that some of the technology Kang will need gets invented (Tony's time travel machine). As he gamed this particular fight over and over, maybe more than 15 million times, He Who Remains chose this specific set of events. He caused Heimdall, Loki, Gamora, Black Widow, and Iron Man to die.
Thanos was the big bad leading up to the stunning double bill of Avengers: Infinity War and Avengers: Endgame, and the current villain in phase five is Kang the Conqueror, though questions remain around his future involvement in the MCU due to assault charges leveled against Jonathan Majors, who plays the complicated ...
The Time-Eater ranks atop the most powerful Kang variants thanks to his assuming Galactus' power. This variant killed Galactus and absorbed the Power Cosmic.
Kang has always been one of Marvel's most powerful villains, a time-traveler who had conquered the world but went back in time to assure it would happen regardless of the timeline. He has taken the Avengers to the limit more than once thanks to his access to technology from the future.
But other than that, to be perfectly honest, Kang simply doesn't have the presence Thanos had to make him seem like the overarching threat. Kang was rather hyped only to be rather taken down a notch: Kang the Conqueror has not been removed from Marvel.
Thanos isn't a cosmic being; instead, he's just another mortal who's very hard to kill. Therefore, Korvac is someone who is stronger than Thanos and sits above him in the pecking order.
Hailing from the Dark Dimension, Dormammu made it his goal to infiltrate the MCU and take control of it. Only the Sorcerer Supreme stands in his way and thanks to Doctor Strange and the Time Stone, he was defeated - for a time. His powers are off the charts and comparable to a god so he is easily stronger than Thanos.
Matthew Waterson noted to Phase Zero that Thanos' Infinity Gauntlet is metal, suggesting that Magneto could have easily stripped Thanos of his most powerful weapons, rendering him all but powerless, and making him easier to take down.
Kang the Conqueror may be the strongest villain in the MCU yet. But one Eternal can stop him if he can survive long enough to face him. Kang's growing presence in the Marvel Cinematic Universe has inadvertently disadvantaged many of its heroes before they've even met him.
Disabling his suit could potentially strip him of his technological powers and weaken him. Ant-Man has already shown the ability to sabotage technologically-advanced suits like he did with Falcon and Iron Man in previous movies. This could be a key advantage in defeating Kang.
His divine origins and his status as "the God of Strength" make Hercules so powerful that he can rival or surpass even the mightiest Avengers such as Thor or Hulk. However, the Prince of Power has another, more subtle, ability that turns out very useful against masters of time travel such as Kang.
