The Avengers are supposed to be Earth's Mightiest Heroes. They're the group of individuals that stands up for those who can't fight for themselves. Despite this, The Avengers have done some pretty terrible things in their days, especially to one another.
Be it an argument about their place in the world, which turns into a war or straight-up murdering each other; these are just ten of the worst things that Avengers have ever done to one another.
10 10) Iron Man convincing Spider-Man to reveal his secret identity
While Tony Stark and Peter Parker have a father/son dynamic in the MCU, they're more casual friends in the mainstream comics.
During the Civil War storyline, Stark needed a hero to come forth and reveal their identity in support of the Super Hero Registration Act. So, he was able to convince Spider-Man that doing so was a good idea... except it wasn't. Not only does Peter's worst fear of his foes attacking his loved ones come to fruition (Aunt May is shot), but the poor guy is nearly beaten to death.
It was a move so bad that Spidey had to make a deal with Mephisto to undo all of these events.
9 9) Starting a War with the X-Men
In Avengers vs. X-Men, we see the Phoenix Force returning and, according to Wolverine, it's setting its sights on Hope Summers. When Captain America comes and tries to ask Cyclops to hand the girl over, the X-Men leader doesn't cooperate with the leader of the Avengers. So, does Cap try to work things diplomatically with the X-Men? No, he summons the team to go with war with the mutants.
Seeing how the X-Men are heroes who stand up for Mutant Rights, it's a pretty dirty move for the Avengers, who stand for diversity, to go against a minority group.
8 8) Wolverine insulting Hawkeye about his dead family
If you've seen both Age of Ultron and Endgame, you already know that Hawkeye has a family. While the purple archer doesn't have one in the mainline comics, he did have one in the Ultimate universe, which they were based on.
While MCU Hawkeye got his family back after Thanos snapped them away, Ultimate Hawkeye wasn't so lucky and lost his family in Ultimates 2. Like his big-screen counterpart, Ultimate Hawkeye becomes far more violent and angry; making him more of a liability to the Ultimates.
In Ultimates 3, When questioning if Wolverine's information about Quicksilver can be trusted, Wolverine replies with, "Didn't you used to have a family?" While Hawkeye had done plenty of insane things in Ultimates 3, Wolverine didn't need to try to insult him like that. It doesn't even make sense; One person asks if you can be trusted, and you respond by saying, "Oh yeah, well your wife and kids are dead?"
7 7) Sending Hulk to another Planet
The Hulk is not only the strongest teammate on the Avengers but he was even a founding member. So, you'd think the team would treat the green goliath with a little more respect than tossing him into space.
When a gamma bomb causes the Hulk to lose control and level half of Las Vegas, the Illuminati(which Iron Man, Namor, and Dr. Strange are members of) decide that the best course of action is to get the Hulk into a rocket ship and blast him into space. This backfires spectacularly as not only does the Hulk return, but he brings with him an army to get revenge on those who banished him.
6 6) Yellowjacket's Violent Rages
One of the most iconic and controversial moments of Marvel Comics is brought to us from issue #213 in 1981. Earlier in the comics, Hank Pym accidentally causes a chemical spill on him, and it transforms him into Yellowjacket.
As Yellowjacket, Hank is far more deranged and prone to acts of violence. In this infamous comic, The Avengers discuss whether they should remove Yellowjacket from the Team, sending Hank in a fit of anger. Janet tries to calm him down, but he ends up smacking her to the floor. It's later revealed in The Unstoppable Wasp that Hank also had Bipolar Disorder.
5 5) Hawkeye killing Bruce Banner
Civil War II already started as a pretty divisive series, but it also featured this infamous death sequence.
When the Avengers confront Bruce Banner, it's revealed that the good Doctor has been experimenting on himself to keep the Hulk. At this point, it seemed like he was successful, as he hadn't Hulked out for a year. But once he learns the Avengers have hacked his files and are planning to arrest him, he starts getting angry. Before he can Hulk out, Hawkeye shoots an arrow and kills him.
4 4) Creating Ultron
Oh Ultron, you magnificent evil-doer. When Hank Pym (or Tony Stark, if you're only watching the MCU) creates an A.I to help humanity, the A.I instead sets its sights on attempting to eliminate the human race.
In the original comics, Ultron had attacked Hank and erased his memories, while the robotic menace slowly started to upgrade itself into Ultron 5. Ultron then creates Vision and has his new creation upgrade his master to Ultron 6, which is now covered in adamantium, the same metal that Wolverine's unbreakable claws are made out of.
3 3) Starting Civil War with each other... Twice
When a group of superheroes (or Scarlett Witch, if you're familiar with the MCU) inadvertently causes the death of dozens of people, the government wants superheroes to register with them.
While some agree that even heroes need to be kept in check, others, like Cap, say that heroes shouldn't be at the whim of the US Government when innocent people are in trouble. This ultimately leads to a war within the superhero community.
While it's a topic that deserves to be discussed, we didn't need heroes to fight against each other. If that wasn't bad enough, the Avengers again went to Civil War with each other in 2016 when Captain Marvel and Iron Man are at odds in deciding what to do with an Inhuman that can predict the future.
2 2) Scarlett Witch killing Multiple Avengers
The Avengers are heroes that only resort to killing villains when they have no other choice. Even if they are forced to do this deed, it can be argued that they did it to people who deserved it. However, that argument goes out the window when it's heroes killing heroes.
In Avengers Disassembled, we see Scarlett Witch killing multiple members of the team in what Dr. Strange believes is an attempt at revenge for the death of her children. She is assumed to have killed Ant-Man (who is later revealed to be saved by his daughter), she makes She-Hulk rip Vision in half, and she summons a Kree armada, with one soldier attacking Hawkeye's explosive arrows, causing them to explode and kill him.
Scarlet Witch's actions were seen as so out of left-field that in Avengers: The Child Crusade, it was reconned by Dr. Doom saying that he was behind this all and Baron Mordo was influencing Dr. Strange. However, Doom isn't one of the more trustworthy people to listen to.
1 1) Ignoring It When Carol Danvers Was Abused by Marcus
It's the comic even the writers of it hated what they did. In Avengers #200, The team returns from a mission to find that then Ms. Marvel, Carol Danvers, had become pregnant in a matter of hours. How did this happen? Well, a character named Marcus (son of the villain, Immortus) used his reality-warping powers to abduct Ms. Marvel, mind control her into loving him and then impregnated himself into her womb as a way to come to earth. He then wiped her memory clean of the event, and she "willingly" went with him to another dimension to lead a happy life. And the Avengers... treated the whole thing as a trivial inconvenience.
It was so terrible that Ms. Marvel writer, Chris Claremont, wrote Avengers annual #10 to haver tell the Avengers off and joined the X-Men. While Carol and the Avengers have made up since then, it's still the absolute worst thing that the team has ever done to one of their own.