Dubbed "Earth's Mightiest Heroes," the Avengers are the most well-respected team in the Marvel Universe, having protected the Earth—and the universe—since 1963. The Avengers have earned the world's respect by triumphing over the greatest adversaries imaginable time and time again. They have become a prestigious organization that young superheroes dream of one day joining. One of the reasons the Avengers are so successful is that they trust each other.

When Captain America, Iron Man, and Thor go into battle they all know they have each other's backs. Many of these heroes have been with the team for so long that being an Avenger is a part of them now, something that they value far too much to ever betray.

However, not all Avengers feel the same way, and some who feel that way now didn't in the past. There were even a few who proved that they were never worthy of the title of "Avenger." Who are these traitors? Let's have a look at 15 Avengers Who Betrayed The Team.

15. Hulk

Hulk and Namor vs. Avengers

As one of the five founding members of the Avengers, the Hulk is featured as part of the core group in the films, the cartoons, and the merchandise. To anyone who doesn't read the comics, it would be perfectly understandable to think that the Hulk is an important part of the team, when in fact, he quit the Avengers at the end of the second issue because he felt that the Avengers secretly hated him.

In the very next issue, he met Namor the Sub-Mariner, who wanted to use the Hulk to destroy the Avengers since there was no way he could do it alone. The Hulk, still angry at his former teammates, agreed and the two joined forces, all the while plotting to betray each other after the battle was over. The two gave Iron Man, Thor, and Giant-Man all they could handle, but in the end the Hulk was turned back into Bruce Banner, thus making it impossible for Namor to win.

14. Sandman

Spider-Man and Sandman team up in Marvel Comics

Flint Marko is one of Spider-Man's oldest enemies, having first fought the wall-crawler in The Amazing Spider-Man #4 in 1963. As "The Sandman," Marko fought Spider-Man by himself, alongside his partner Hydro-Man, and with the Sinister Six. He was also a member of the Frightful Four.

Over the years, Sandman went through a change. An encounter with the Thing in the 1980s caused Sandman to rethink his life choices and go straight. Sandman remained on this path for several years, and in 1991 Captain America announced to the public that Sandman would be joining the ranks of the Avengers as a reserve member. Knowing Sandman's history, the public was shocked, but Cap trusted that Sandman had changed his ways. As an Avenger, Sandman never went on active duty but he came to the Avengers' aid whenever he was called.

In 1999, Sandman turned his back on his fellow heroes and joined up with his old partners from the Frightful Four, Wizard and Trapster. Sandman used the trust he had gained with Spider-Man to his advantage, allowing him a chance to take him by surprise. In returning to his villainous ways, Sandman not only betrayed Spider-Man but the Avengers as well, causing his membership to be revoked.

13. Hawkeye

Though not a founding member, there may be no other character among the Avengers' ranks more loyal to the team than Hawkeye. While the Thor, Iron Man, and Captain America are often counted as the Avengers' most important members, all three have their own problems to deal with, problems that sometimes take them away from the Avengers. For Hawkeye, however, being an Avenger is part of his identity and something he cares deeply about.

In the early '70s, Hawkeye wasn't quite there yet. After enduring several rejections from the Scarlet Witch, Hawkeye tried to win back his ex-girlfriend, the Black Widow, from her current boyfriend, Daredevil. The Avengers arrived to stop Hawkeye and Daredevil from fighting, causing Hawkeye to quit the team. Not too long after this, Hawkeye became entangled with the Defenders. When Loki and Dormannu deceived the two into fighting each other, Hawkeye was torn, as he was the only Defender with strong ties to the Avengers. He ultimately sided with the Defenders and managed to defeat Iron Man. When the deception was discovered, Hawkeye was forgiven.

12. Wonder Man

Wonder Man in Marvel Comics

The ionic-energy-powered superhero, Wonder Man, has a deep history with the Avengers that goes all the way back to his debut in Avengers #9 in 1964, the same issue in which he died. Wonder Man was resurrected years later and has become a staple of the Avengers ever since, either serving with the main Avengers team or the West Coast branch. He was also involved in Civil War, in which he was a crucial player for Iron Man's side.

During the late 2000s, we began to see less of Wonder Man as an Avenger. When he did appear, he was shown to be more aggressive and hateful toward his former teammates. He believed that the Avengers were a disease that was destroying the world instead of making it better. The tension between Wonder Man and the Avengers came to a head when he gathered a team called the Revengers, a small group of heroes and villains with bitter feelings towards the Avengers. Wonder Man led his team in an assault on the Avengers. When Wonder Man was defeated, it was determined that his ionic energy was having an effect on his brain. When he was finally cured, Wonder Man apologized for the trouble he had caused.

11. Vision

The Vision has been an Avenger since the iconic issue of Avengers #57 in 1969. A constant of the team, Vision is a character who has experienced tremendous character growth since his introduction. Though an android, Vision's capacity for humanity was first witnessed when he was seen shedding a tear at the end of Avengers #57. The Vision has dealt with many problems concerning his emotions, many of which involved his feelings for the Scarlet Witch.

Vision's difficulties with balancing his emotions got the best of him after he became leader of the team. In trying to create world peace, Vision tried to take control of the world's computers and defense systems. He was opposed by the Avengers, who had to launch an attack on their own headquarters to defeat him. Vision eventually realized his mistake and tried to atone for his crime, but the damage was already done. Vision's actions cost the Avengers the trust of the federal government.

10. The Protector (Noh-Varr)

Noh-Varr attacks in Marvel Comics.

Noh-Varr is a Kree soldier who sided with Earth during Secret Invasion. After taking the name "Captain Marvel"--the same name used by the Kree hero Mar-Vell—he joined Osborn's Avengers. After leaving the team, he became a member of the official Avengers team as "The Protector." He served them well for a time, until Avengers vs. X-Men which saw the world threatened by the coming of the Phoenix Force. The Avengers needed all hands on deck, meaning it was a bad time for one of their own to turn traitor.

The Avengers didn't know that the Supreme Intelligence—the computerized brain that governs the Kree—gave the Protector orders to deliver a piece of the Phoenix Force once it was contained by the Avengers. The Protector followed the Supreme Intelligence's orders and turned his back on his teammates. When he learned that the Supreme Intelligence intended to allow the Phoenix Force to destroy Earth, the Protector chose to betray the Kree as well. Unfortunately for him, it was too late to go back to the Avengers, who forbade him from ever returning to Earth.

9. Swordsman

Swordsman in Marvel Comics

The Swordsman was Hawkeye's mentor and a criminal who tried to join the Avengers so that he could take advantage of the benefits. When they turned him away, he was approached by Iron Man's archenemy, the Mandarin, who gave him a new sword and a mission: to infiltrate the Avengers and destroy them from the inside. Mandarin engineered a plot to trick the Avengers into thinking that Iron Man had vouched for the Swordsman. The ploy worked, and Swordsman was allowed entry, but not without gaining the suspicion of his new teammates.

Swordsman planted a bomb in Avengers' Mansion, just as he was told, but began to have second thoughts. When he tried to remove the bomb, he was caught by Captain America and forced into a fight. Despite the Swordsman's betrayal, years later he was forgiven and welcomed back onto the team, alongside his wife, Mantis.

8. Quicksilver

Quicksilver from the X-Men

In 1986, the East and West Coast Avengers were playing baseball when they received a surprise visit from Freedom Force, a group of X-Men villains released from prison to work for the government. Mystique, leader of Freedom Force, announced to the Avengers that they were to be arrested for treason. After a fierce battle with Freedom Force, Captain America agreed to surrender. At a hearing, the Avengers were told that someone had obtained proof that Vision's attempt to gain control over the world's computers was actually a plot engineered by the Avengers themselves. The Avengers demanded to know who their accuser was, and after much suspense, the traitor was revealed: Quicksilver.

Quicksilver was extremely troubled at the time due to his rocky marriage with the Inhuman, Crystal. After discovering that Crystal had an affair, Quicksilver was enraged. He wanted revenge on everyone who had wronged him. Maximus the Mad found Quicksilver and manipulated him into somehow believing that the Avengers were responsible for his predicament. After defeating Quicksilver, he was returned to the Inhumans and eventually restored to his normal state of mind.

7. Doctor Druid

Doctor Druid and Ravonna from Avengers comics

Doctor Druid is a sorcerer who practices Celtic magic that he picked up from the Ancient One. His magical abilities are overshadowed by another of the Ancient One's pupils, Doctor Strange. Though he may seem like a minor character, his effect on the Avengers is anything but that.

Doctor Druid joined the Avengers after Baron Zemo's Masters of Evil destroyed Avengers' Mansion. His assistance in defeating Zemo was what led to the decision to grant him membership.

Doctor Druid's life took a turn for the worst when he began having visions of a beautiful woman named Ravonna. Ravonna preyed upon his arrogance and weakness for women in order to manipulate him into doing her bidding. She had him convinced that it should be he who leads the Avengers. So Doctor Druid used his powers of telepathy to influence the Avengers into making him their new leader.

Doctor Druid colluded with Ravonna to manipulate the Avengers into retrieving a powerful weapon. He telepathically controlled She-Hulk and made her fight the Avengers. When his plan failed, Doctor Druid and Ravonna were lost in a timestorm. Shaken by what she had done to her teammates, She-Hulk quit the team, and the only two Avengers left—Thor and Black Knight—disbanded the team.

6. Moondragon

Thor drinking wine with Moondragon

1976, the telepathic human daughter of Drax the Destroyer joined the Avengers, using her mind powers to assist them in a number of adventures. Her abilities allowed her to influence the emotions of others, causing them to feel things they otherwise never would.

Moondragon eventually found a planet full of people she believed needed her. Calling herself a goddess, she used her powers to force them into living in peace. Drax discovered what she was doing and convinced the Avengers to assist him in stopping her. Knowing that she would need help to maintain her rule, Moondragon used her mental powers to rape Thor. After making him love her, she used him to hold off Drax and the Avengers.

Moondragon killed Drax, but was soon defeated by the combined efforts of the Avengers. Free of Moondragon's control, Thor took her to Odin where she could be judged as a "goddess," since that was how she saw herself. Odin forced her to wear a headband that negated her abilities, and appointed Valkyrie as her guardian to keep her in line.

5. Scarlet Witch

Scarlet Witch Avengers Disassembled

Only a few heroes can claim to have served the Avengers more than Wanda Maximoff. She has been a constant of the team since the day she joined back in 1965. When not seen with the main Avengers team, she was with Hawkeye's West Coast branch in the 1980s. She was often accompanied by her husband, the android Avenger known as the Vision.

The pair had two kids, despite how impossible it may have seemed. It was later revealed that it actually was impossible. The children were created by Scarlet Witch's reality-warping powers, meaning that they were never real. This realization slowly drove her insane. When she finally snapped in Avengers Disassembled, her powers set in motion events that caused the deaths of Hawkeye, Ant-Man (Scott Lang), Jack of Hearts, and Vision, her own husband. When the Avengers discovered that they were being ripped apart from the inside by one of their own, they allied with Doctor Strange to stop her from hurting anyone else. When the threat was dealt with, the Avengers handed her over to her father, Magneto.

4. Sentry

Sentry's in full costume surrounded by smoke and lightening

After the events of Avengers Disassembled, Captain America found himself in a position where it became necessary to put together a new team of Avengers. With many of the team's core members and mainstays, Captain America had no choice but to think outside the box, leading him to recruit a completely new kind of Avengers team, one that included Spider-Man, Wolverine, and a Superman-like character called the Sentry. The Sentry was the team's powerhouse, fighting alongside the Avengers on a number of missions.

Sentry was supposedly one of the most powerful heroes in the Marvel Universe, but despite his power, Sentry was not without his flaws. He believed that his archenemy was an evil entity called the Void, but in actuality the Void was another side of the Sentry's personality, a side he subconsciously hid from himself. Sentry was visited by Norman Osborn, who promised to help with his condition. Sentry joined Osborn's Dark Avengers and assisted him in the attack on Asgard. When Loki switched sides to help the Avengers, Sentry killed Loki, thus earning the wrath of Thor. Calling Sentry a traitor to everything that the Avengers stand for, Thor killed Sentry and took his body to burn in the sun.

3. Hank Pym

Hank Pym AKA Yellowjacket slapping Janet Van Dyne away in Marvel comics

As "Ant-Man," Hank Pym and his fiancé, the Wasp, played an important role in establishing the Avengers as a team. Throughout his tenure, readers saw Pym become "Giant-Man," "Goliath," and finally, "Yellowjacket." He was also responsible for the creation of Ultron. But Ultron has nothing to do with Pym's betrayal. Though the exact cause of it is debatable, we know that Hank Pym at some point become emotionally unstable and had trouble controlling his anger. After using unnecessary force against an enemy, Captain America called for a hearing.

Fearing what the Avengers might decide, Pym developed a plan to prove his worth. He built a powerful robot that only he could destroy and sent it to attack the Avengers. When the Wasp discovered the plan, he hit her. This scene has since become one of the most talked-about moments in Avengers history. (This punch was later revealed to be a mistake by the artist  who turned what was supposed to be a shove into a right cross.)

Pym's plan with the robot went horribly wrong,  costing him the Avengers' trust, thus making it easy for Egghead to frame him for something he didn't do. Pym was sent to jail, and not even his own teammates believed he was innocent.

2. Iron Man

Published in 1988 in the pages of Iron Man was an eight-part event called "Armor Wars," that saw Iron discover that someone was stealing his designs, and it was up to Iron Man to find out who it was and stop them.

Iron Man turned his attention to the Guardsmen, security officers with armor designed by Tony Stark. The Guardsmen were in charge of protecting the Vault, the prison where most superpowered criminals were kept at the time. Deciding that the best thing was for no one to have access to his tech, Iron Man tried to neutralize the Guardsman but ended up causing a mass breakout at the Vault, a mess that had to be cleaned up by Steve Rogers.

No longer going by the title of "Captain America," Steve Rogers had just been given a new shield by Stark to replace the original. After the breakout at the Vault, Steve returned the shield, feeling that it was a gift intended to make Steve look the other way. Steve demanded that Stark turn himself in, resulting in a fight that Steve was unable to win without a weapon.

For his actions in the Armor Wars, Iron Man was expelled from the Avengers.

1. Captain America

Captain America Hail Hydra

Captain America has been the embodiment of the Avengers since he joined the team in Avengers #4. Nothing says "The Avengers" like Captain America. He's such an important part of what the Avengers stand for that he's been given "Founder" status despite not actually being a founding member. So could any betrayal hurt the Avengers more deeply than Captain America's? Is Captain America turning on the Avengers even a possibility?

A year ago, it would certainly seem impossible, but since Cap's memories were rewritten by the Cosmic Cube, we've seen the Sentinel of Liberty become an agent of HYDRA, an organization he has spent his life trying to destroy. Since then, we've seen Cap working in the shadows to engineer some master plot that will shake the Marvel Universe to its core.

In the Secret Empire event that's currently unfolding, we'll see the Avengers rocked by this shocking betrayal that no Avenger ever would have expected. Emotionally speaking, it will cut deeper than anything any of the Avengers have ever done. We can only hope that Cap won't be able to match Scarlet Witch's body count in Avengers Disassembled, but somehow that seems unlikely.