Marvel's heroes are some of the more complicated heroes in all of comics. This was their claim to fame when they were first introduced and it's helped make them into some of the most respected heroes in comics. While they aren't as pure as many other heroes, they still have principles and values that they work to uphold.

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Over the years, things have gotten less black and white, forcing many heroes to compromise their values in ways in order to save the day. Sometimes it's by choice and other times it's because of outside influences but it usually makes for interesting storytelling.

10 Spider-Man Sacrificing His Marriage To Save Aunt May Was Him Shirking His Responsibility

Spider-Man One More Day

While Marvel editorial claimed the retcon was a heroic act of sacrifice on the part of Spider-Man and Mary Jane, it's actually anything but. Spider-Man's whole thing is about responsibility and instead of taking responsibility for the actions that led to May's shooting, he tried to find another solution.

May was shot because Spider-Man revealed his secret identity on TV. Instead of taking responsibility for this action and letting things play out as they should, he gave up his marriage and let Mephisto literally change reality so he wouldn't have to face the consequences of his actions.

9 The Beast Has Made A Science Of Trampling On Everything He Was Taught

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The Beast was once the X-Men's funny science guy, a mutant who looked like a monster yet was an erudite, friendly man. Something changed in the Beast around the time Cyclops and Wolverine had their fight. He joined the Illuminati, brought the original five X-Men from the past to the present, and basically started acting like a completely different person.

That kicked into overdrive when he was made head of X-Force on Krakoa. He transformed an entire country into a Petri dish for his experiments, a move which came back to bite him, and has done a lot of bad things in the name of protecting mutantkind, many of which he didn't need to do.

8 Professor X's Mindwipe Of Magneto Was An Act That Had Grave Consequences

Professor X vs Magneto

Professor X has always been a bit free with using his mental abilities. He messed with people's minds in a lot of little ways but he never out and out erased someone totally. It was a step he'd eventually take after Magneto tore the adamantium from Wolverine's skeleton. In retaliation, Professor X mindwiped Magneto in order to end his threat and save lives.

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Unfortunately, this led to the birth of Onslaught, as something inside Magneto planted itself inside Professor X. Not only did Professor X betray his values, the consequences of his actions almost destroyed the Marvel Universe.

7 Bucky Was Transformed Into The Winter Soldier By The Soviet Union

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In World War II, Captain America was the Allies' greatest hero but he couldn't have done without his partner Bucky. Cap and Bucky were a nearly unstoppable pair and together they dealt blow after blow to the Nazi war machine. One fateful day, their luck and skill would run out as they struggled to stop a drone bomb launched at London.

Cap ended up frozen in ice and everyone thought Bucky was dead until he reappeared as the Winter Soldier. The Soviets found him and nursed him back to help, transforming him into a brainwashed assassin. Only with Cap's help was he able to break free and become a hero again.

6 The Sentry Went From Golden Guardian Of Good To Norman Osborn's Lapdog

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The Sentry was one of the most powerful heroes on the planet and, at the beginning of his career, one of the greatest. The Golden Guardian of Good was friends with the Fantastic Four and the Avengers, knew the original X-Men, and his golden aura soothed the Hulk. After discovering his arch-enemy Void was a part of him, he volunteered to have his memory erased from the world.

His return years later would see him learn the circumstances of his origin and get another chance at being a superhero. When Norman Osborn took over the Avengers, the Sentry stayed with the team and was manipulated by Osborn, becoming more and more inhuman until he released the Void completely and had to be put down by the Avengers.

5 The Illuminati Are Responsible For Countless Deaths

Avengers Illuminati Iron Man Reed Richards Dr Strange Hickman

The Illuminati was always a bit of a bad idea but things only got worse for the group as time went on. A secret grouping of the greatest leaders in the Marvel Universe including Mister Fantastic, Iron Man, Namor, Doctor Strange, Black Bolt, and others, the team made a lot of decisions that turned out to be pretty bad.

Their most destructive acts came during the Incursions, as they stopped at nothing to save their Earth at the cost of all others, committing genocide on a massive scale. The number of deaths they caused are incalculable and rival even Thanos's body count.

4 Hawkeye Ended Up Killing The Hulk

Hulk Death Civil War II

Civil War II by Brian Michael Bendis is considered one of the worst Marvel events of the 21st century but it did serve as the beginning of a good story down the road. At one point, the assembled heroes confronted Bruce Banner, who Ulysses's prediction powers said was going to kill Iron Man. He hadn't been the Hulk for a long time but asked Hawkeye to help him.

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Unbeknownst to everyone else, Banner had given a Hawkeye an arrow that could kill him years before and when Banner asked him to help, Hawkeye shot him in the eye. The arrow worked but eventually, Banner would return as the Immortal Hulk, a possibly greater monster than before.

3 Iron Man Betrayed Friends And Worked With Villains To Win During Civil War

Captain America vs Iron Man during Civil War

Iron Man has long been one of Marvel's shadiest heroes but his actions in Civil War take the cake. Coming out as pro-Registration, Iron Man proved he was ready to do anything to win. He betrayed his friends, almost beating Cap to death at one point, and recruited villains to join the Thunderbolts and work with the heroes on his side.

Iron Man went full fascist during Civil War, betraying everything he stood for in order to achieve his goals. His actions would tarnish his already dirty reputation even more and cause a lot of very bad things to happen.

2 Cyclops Became More Desperate As Things For Mutants Got Worse, Eventually Falling To The Power Of The Phoenix

CycloCyclops as Dark Phoenix vs the X-Men and Avengersps as Dark Phoenix vs the X-Men and Avengers

The time after M-Day, when Scarlet Witch depowered the vast majority of the mutant race, was terrible for the X-Men and especially their leader Cyclops. Now the leader of an endangered species, Cyclops would be slowly ground down by the lengths he had to go to in order to defend mutants. With the coming of Phoenix, he made a plan that was thwarted by the Avengers and ended up gaining the power of the Phoenix.

As told in Avengers Vs. X-Men, the power went to Cyclops and the rest of the Phoenix Five's heads and eventually, Cyclops would be the last one standing with all the power of the Phoenix at his disposal. After killing Professor X, he went full Dark Phoenix, forcing the Avengers and X-Men to team up to stop him.

1 The Cosmic Cube Gave Captain America Back His Youth But Also Made Him A Member Of Hydra

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Captain America is kept young by his super-soldier serum but it has been known to peter out at times. One of those times ended up almost dooming the Marvel Universe. While he would get his youth back thanks to the young girl Kobik, a sentient Cosmic Cube, she was programmed by Red Skull to change Cap's past and make him a member of Hydra.

This new Hydra-aligned Captain America would enact a grand scheme to give himself and Hydra power. His plan would work and it would take the old Cap, still inside of the Cosmic Cube, to stop the Hydra version of himself.

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