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.
Maybe it's due to trust issues. In the Marvel universe, they've had their share of disagreements and betrayals. If in the fanfiction, some past secrets come to light, for example, Steve finding out Tony had been withholding information about a potential threat because he thought Steve couldn't handle it. This lack of trust could lead to a divorce.
Natasha Romanoff would be disappointed. She values the unity among the Avengers and sees Tony and Steve as important pillars of that unity. She might try to mediate at first, but if the divorce is inevitable, she'd be sad to see the team's dynamic change so drastically.
One possible reason could be differences in their superhero duties. Maybe their approaches to saving the world clashed so much that it put a strain on their relationship. For example, Tony might be more into high - tech solutions while Steve prefers a more traditional, hands - on approach.
One reason could be a misunderstanding during a battle. Maybe Steve made a strategic move that put Tony in danger without realizing it fully. Another might be that Steve said something harsh in the heat of an argument, like criticizing Tony's technology when it was actually saving lives. Or perhaps Steve made a promise to Tony and failed to keep it, which made him feel guilty and led to the apology.
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.
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.
The plot could start with Steve realizing that his bond with Bucky is stronger than his relationship with Tony. Maybe there have been some misunderstandings or conflicts between Steve and Tony that make Steve reevaluate his feelings. Then, Steve decides to break things off with Tony in a rather dramatic way. After that, it could explore how Tony reacts to this rejection, and how Bucky fits into the new dynamic between Steve and the rest of the Avengers.
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 that they grew apart over time. Maybe their different responsibilities in the demigod world led to a lack of communication and connection. Another reason could be external pressures, like the expectations of their respective families or the demigod community. It could also be that they had different ideas about how to raise their child, which caused irreconcilable differences.
Perhaps he leaves for personal growth. America has become a place full of painful memories for him, like the loss of friends during battles that happened on American soil. So, he decides to start anew in another place.