Perhaps Tony Stark's sense of self - sacrifice led to his 'betrayal'. He might have believed that by taking a certain action that others would consider a betrayal, he could prevent a greater disaster. His over - confidence in his own plans could also play a part. He thought he had a foolproof plan to save the day, but it involved actions that went against the trust of his comrades.
He could have been betrayed first. Maybe his friends or the Avengers turned on him in some way, and in his anger and hurt, he retaliated in a way that was seen as a betrayal. It's also possible that he was misled by false information. He thought he was doing the right thing, but it turned out to be a betrayal because the information was wrong. For instance, he might have been told that a certain action would save the world when in fact it was harmful.
One possible reason could be that he was forced to betray under some kind of mind control. Maybe an enemy like Hydra got hold of him and made him do things against his will. Another reason might be that he was trying to protect something or someone he loved in a very extreme way that seemed like a betrayal to others. For example, he might have made a deal with a villain to keep Pepper safe.
Steve Rogers would probably be deeply disappointed. He values loyalty highly, and Tony's betrayal would shatter the trust they had. He would try to find out the reasons behind it and might even try to bring Tony back to the right path if he thought there was a chance.
One possible plot reason could be ideological differences. Tony Stark is often portrayed as a tech - savvy capitalist, while Steve Rogers has more traditional values. Their views on how to protect the world, like Tony's preference for high - tech solutions and Steve's leaning towards more human - centered approaches, might drive them apart to the point of divorce in the fanfiction.
One possible reason could be a disagreement over superhero tactics. Peter, being young and idealistic, might yell at Tony if he thought Tony's methods were too extreme or not in line with his own sense of justice. For example, if Tony made a decision during a battle that put civilians at risk, Peter would likely be very vocal about it.
Maybe he realizes that the cost of being Iron Man is too high. His suits are constantly damaged, and he has to deal with numerous enemies. This could lead to him quitting in the fanfiction to avoid further harm to himself and those around him. For example, his suits might put Pepper Potts in danger, so he decides to stop.
One reason could be that he's frustrated with the leadership or the direction the Avengers are taking in the fanfiction. He might feel his ideas are not being heard.
One possible reason could be a misunderstanding. Maybe Inuyasha misinterprets Kagome's actions or words. For example, if Kagome is trying to help a new character who seems to have a connection to the Shikon Jewel, Inuyasha might think she's being disloyal and thus betray her. Another reason could be some sort of dark influence. There could be an evil force that makes Inuyasha act out of character and turn against Kagome.
Guilt. For example, if he fails to save someone he cares about. He'll feel responsible and that could lead to him crying.
In fanfiction, emotional distress can also be a factor. If something really bad happens, like the loss of a loved one or the destruction of his work that he has put so much effort into, the shock and grief could be so overwhelming that he faints. Additionally, he could be suffering from some hidden illness that flares up suddenly and causes him to faint.
Maybe he doesn't fully understand his powers yet. Tony Stark is a scientific genius, but new powers might be beyond his current understanding. He could be worried that if he reveals them too soon, he won't be able to control them properly and might cause harm. So, he chooses to hide them while he studies and figures them out.
In some fanfiction, Tony Stark might be angry at the Avengers because of a perceived betrayal. For example, if they made a decision without consulting him that put him or the world in danger. He's a control freak in a way, so when things go awry without his input, he could get mad.