The sprawling Marvel franchise is about to release its most anticipated film yet, Doctor Strange and the Multiverse of Madness. Throughout the MCU, their legendary heroes go up against a number of villains over the years. Some are incredibly memorable, like Vulture, and some are less so, like Whiplash. Many MCU films had their heroes go up against villains with very similar abilities in order to attempt to create dark parallels to them.
This trope wore thin pretty early on and the MCU has course-corrected away from this, but that's not to say these villains didn't have their place. While they may not be the most inventive antagonists, they served an important purpose in growing the franchise and they proved to be just as strong as some of Marvel's favorite heroes.
Iron Monger
In Iron Man, Jeff Bridges plays Obadiah Stane and it's revealed that he hired the Ten Rings terrorist group to capture Tony so that he could take over Stark Industries. When Tony comes back with a suit of armor and miniature arc reactor, Stane builds his own suit of armor to take him down.
Stane was the first instance where a villain shared a similarity to the hero, and the first instance of a famous MCU name-drop. His suit of armor was based on Tony's MKI armor, but bigger and with more weapons. Stane served to remind Tony what kind of man he could have become if he didn't become Iron Man.
Red Skull
Red Skull ran 's science division, Hydra, in World War II. A secret entity that was building weapons to conquer the world using the power of the Tesseract, Red Skull would get close to realizing his dream; however, Captain America was able to stop him just in time. Red Skull could match Captain America's powers but was unable to withstand the power of the Tesseract.
The same serum that gave Captain America his abilities also gave Red Skull abilities. Red Skull was an evil man before the serum, so when he was injected, it heightened what was already there and turned him into a monster. If Steve wasn't such a good man, he could have become just the same as Red Skull.
Abomination
The Abomination started as Emil Blonsky, a soldier who worked with General Ross to track down Bruce Banner/The Hulk. In order to help Blonsky, Ross injected him with the same serum that turned Banner into The Hulk. The Incredible Hulk ends with Blonsky turning into the Abomination, a sadistic perversion of the Hulk.
The Abomination was recently seen in She-Hulk. But in The Incredible Hulk, he serves as a good introductory foil for the green goliath. He matches Hulk's speed and strength but is willing to do anything to stop his foe.
The Winter Soldier
Hydra was revealed to have infiltrated S.H.I.E.L.D. in one of Captain America: The Winter Soldier, and they used the Winter Soldier to operate from the shadows and kill their enemies. Captain America learned that The Winter Soldier is actually his friend Bucky who's been turned into a super-soldier himself.
Bucky is another dark reflection of Steve when he's the Winter Soldier. While he's had a successful redemption arc, his first appearance is that of a tool used by a secret organization. Winter Soldier is equal to Captain America in every way and it's a good thing Steve was able to get through to him eventually.
Yellowjacket
In Ant-Man, Hank Pym hires Scott Lang to perform a heist on Pym Tech. Darren Cross has taken over the company and is about to create an army of shrinking soldiers like Ant-Man and Pym can't let that happen. Cross is able to dress in his prototype suit and become Yellowjacket to fight the new Ant-Man. Scott is able to beat him but almost lost himself in the process.
Yellowjacket uses the same shrinking abilities that Ant-Man uses, but his suit has a few upgrades. Unlike Ant-Man, Yellowjacket can fly and shoot lasers. But outside of that, they're basically the same thing.
Kaecilius
someone who has a defining quote for Phase 3, is trying to stop Kaecilius from taking a book. It's learned that the book reveals a forbidden spell that allows the to open the Dark Dimension and use it to harness the power of Dormammu. But it leaves the Earth vulnerable to an attack from the malevolent ruler of the Dark Dimension.
Like Strange, Kaecilius lost something important to him which led him to the mystic arts. Kaecilius was drawn to the power of the Dark Dimension because he felt it could help bring the family that he lost back. He had more training in the mystic arts than Strange but, in the end, Strange was able to outwit him and his dark master.
Killmonger
Eric Killmonger was the cousin of T'Challa and he enacted a plan that would allow him to enter Wakanda and become its king. Killmonger felt that Wakanda could supply arms to all the marginalized peoples of the world so they can rise up and slay their oppressors. T'Challa didn't feel this was right but knew that Wakanda could still do more anyway.
The villain of Black Panther is often considered one of the best. The philosophical debate at the heart of the film changes T'Challa for the better. When Killmonger becomes king, he also becomes the Black Panther and is able to match T'Challa in battle.
The Mandarin
The Mandarin was thought to be revealed as a fictional character in Iron Man 3, but Shang-Chi and the Legend of the Ten Rings introduced audiences to the real Mandarin. His real name was Wenwu and he wanted to reunite with his long-dead wife by invading the mystical land she came from. Unbeknownst to him, it will actually release the Dweller in the Darkness.
At the beginning of the story, the Mandarin has one major advantage over Shang-Chi, which is that he wields the Ten Rings. Shang-Chi and the Mandarin are both talented martial artists, the best even, but the Ten Rings make him ruthless. When Shang-Chi is able to steal five of the rings, the fight becomes more even, eventually taking the rings for himself.
Loki
Thor introduced the God of Thunder and his brother Loki to the MCU. Loki was seen to descend into darkness due to the fact that he was extremely jealous by Thor potentially becoming the next ruler of Asgard. When Loki finds out he's actually a Frost Giant, he thinks the only way to win over Odin's favor is to destroy the Frost Giants and take Thor out of the equation.
While Loki is a trickster who is able to use magic, and Thor can harness lightning, two Asgardians served the same purpose as something like the Abomination or Red Skull. Loki had a very good and long redemption arc that led to his death, but Thor really proved the kind of threat he could be. Thanks to Tom Hiddleston is sure to get an Emmy nomination.
Agatha Harkness
For Wanda Maximoff's first solo adventure, Wandavision, Agatha Harkness invaded the town of Westview to understand Wanda's powers. Agatha was a witch that was around during the Salem Witch Trials and suspected that Wanda could be the fabled Scarlet Witch that her family warned her about.
This was the first time that Wanda fought a character that was like her. While on paper, the powers of the Scarlet Witch are beyond that of Agatha's, in execution it was still two people with glowing hands shooting vague magic balls at each other.
