The MCU's greatest villain is the mad titan Thanos, who sought to gather the six Infinity Stones to restore balance to the universe at the cost of half its inhabitants. Thanos schemed for years to accomplish this goal, and for years, he sent a wide variety of minions to get the job done, from Loki the trickster god to thugs like Cull Obsidian and Corvus Glaive.
Even with all these minions at his command, Thanos would want to recruit even more agents to his cause, and his cause would appeal to a wide variety of villains from other universes, such as those from the realm of Japanese animation. Anime is populated with many powerful and ambitious villains who would all eagerly join Thanos and fight for him in exchange for power and prestige.
10 Demon Lord Clayman Wants More Puppets (That Time I Got Reincarnated As A Slime)
Demon Lord Clayman embraces an "evil puppetmaster" theme, using and exploiting the people under his command, including the Five Fingers. He also likes to pit his enemies against each other, and he even tried to use a mind-control necklace on Demon Lord Milim Nava.
Clayman was willing to work with Yuuki to get what he wanted, and he would also join Thanos and find a way to build a kingdom for himself in the chaotic post-Snap universe. Clayman would also enjoy bossing around Thanos' other minions.
9 Zaheer Wants Total Chaos (The Legend Of Korra)
Zaheer is an anarchist Airbender and a member of the Red Lotus organization, which is dedicated to overthrowing corrupt kings, queens, and governments to restore the natural order in the world. Zaheer would look at the MCU and quickly criticize organizations such as Hydra, S.H.I.E.L.D., and more. He wants to overthrow all tyrants, good and evil alike.
Thanos' intended Snap threw the universe into chaos and destabilized militaries and governments across the universe, which is exactly what Zaheer wanted. He and the entire Red Lotus organization would gladly fight for Thanos' cause.
8 Akim Would Take This Chance To Harvest New Body Parts (Blood Lad)
Akim the villain is a bit like Frankenstein's monster, a powerful creature who can attach a myriad of body parts to modify himself and gain new powers. He scoured the Demon World in Blood Lad to find new body parts, and if he joined Thanos, he could find even more.
Thanos and his minions fought and killed a wide variety of aliens and people across the universe, and Akim could reach new heights if he took part in all that. He could even take on the Avengers and try to steal their body parts, too, such as Groot's wooden arms or a piece of Thor.
7 Grimmjow Would Take This Chance To Fight Worthy Foes Across The MCU (Bleach)
Grimmjow Jaegerjaques is the 6th Espada, and he has simple but honest motivations. He is driven by instinct, seeking to prove himself the king of the jungle as a panther-like Hollow. He scoured Hueco Mundo searching for worthy foes to devour, and now it's time for a new jungle battlefield.
Grimmjow joined Aizen to gain more power and new enemies to fight, and he'd do the same thing if he heard that Thanos was hiring new minions. Grimmjow would have so much fun invading planets in the MCU and hunting the Stones while also testing himself against truly worthy opponents.
6 Zeref Dragneel Would Seek The Stones For Himself (Fairy Tail)
Zeref Dragneel is an anime villain who sought not to conquer the world but to restore his lost family, especially his brother, Natsu Dragneel. Zeref delved deep into forbidden research to bring back the dead, only to end up as an immortal but cursed and miserable being.
Zeref tried in vain to restore his family in the original story of Fairy Tail, but he might succeed if he joins Thanos to steal the Infinity Stones for his own use. Surely, with such incredible cosmic power, he could be truly reunited with his family at last. It's worth a try, even if it means betraying the mighty Thanos.
5 Envy Would Have Fun Tormenting Thanos' Enemies (Fullmetal Alchemist: Brotherhood)
Envy is a shapeshifting homunculus who is totally loyal to his boss, Father, and he enjoys tormenting and fooling humans to prove the superiority of homunculi. The sadistic Envy gladly incited the bloody Ishval Civil War while in disguise, and he would get another chance to bully humans while under Thanos' command.
If Envy joined Thanos, he could invade countless human-occupied planets and come up with devious ways to fool and betray the humans while searching for the Infinity Stones. Envy could also target intelligent aliens to prove homunculus superiority over them, too.
4 Deidara Could Show Many More People His Art (Naruto)
Some members of the Akatsuki organization seemed to join simply because they had nowhere else to go, and they enjoyed the challenge of hunting the nine tailed beasts to help Pain change the world. Deidara, a rogue ninja with explosive jutsu, would also serve Thanos if he were invited.
Deidara could marvel at many new worlds and cultures across the MCU while fighting for Thanos, then blow them all up with his explosive jutsu. He would also expect Thanos to repay him with glory and riches for all his hard work. After all, artists don't work for free.
3 Sir Crocodile Would Become A Space Pirate (One Piece)
During the Baroque Works storyline, Sir Crocodile the pirate plundered the kingdom of Alabasta to find clues on the Pluton, one of the greatest weapons to ever exist in the One Piece universe. He ran a large and powerful organization, but it's time to join an even greater one.
The power-hungry Crocodile would join Thanos if it meant having an even stronger space pirate crew and opportunities to use even greater weapons of destruction. Crocodile is an opportunist, and Thanos would open many exciting new doors for him across the massive universe. Suddenly, the Grand Line seems so small.
2 Galand Could Crush Many New Enemies (The Seven Deadly Sins)
The mighty Galand would join Thanos' crew for similar reasons as Grimmjow and Deidara - to have fun fighting and slaying many new enemies in glorious combat. Galand was among the most bloodthirsty Ten Commandments, and he just found a new master.
Galand would gladly lead raiding parties on enemy spaceships and capital cities on Thanos' behalf, and he wouldn't stop until the entire enemy army is wiped out. He would hardly even care if he got an Infinity Stone for his troubles or not.
1 Mahito Would Take This Chance To Slaughter Even More Humans (Jujutsu Kaisen)
Mahito is a powerful humanoid curse, and he is convinced that humans are worthless and should be wiped out entirely. Then, curses like him could rule the world in their place, and not even the jujutsu sorcerers can get in his way. But Mahito might need a few more allies to get the job done.
Thanos' invasion of Earth would be a fine opportunity to join the winning side and wipe out countless humans, and Mahito would work alongside Thanos' many non-human minions to finally destroy Homo Sapiens once and for all. He might even try to steal the Infinity Stones for himself.