Maybe he's had some personal losses within the Avengers in the fanfiction, like losing a close friend or seeing the team make a decision that goes against his moral code. This could lead him to want to distance himself from the group. Also, he could be tired of constantly having to save the day and wants a break from the superhero life within the fictional world of the fanfiction.
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.
In the fanfiction, it could be that new characters have joined the Avengers and Tony Stark doesn't get along with them. Or perhaps there have been too many political or bureaucratic issues within the team that he just can't deal with anymore. He may also have found a new purpose outside of the Avengers that he wants to pursue, like focusing on his own scientific research or exploring a different part of the Marvel universe that doesn't involve the Avengers.
Well, in fanfiction, the writers have a lot of creative freedom. 'Tony stark is done with the avengers fanfiction' might mean that the author has reached a point in their story where they feel that Tony Stark's character has completed his journey with the Avengers in their fictional world. It could be a way to introduce a new plotline where Tony goes solo or teams up with other characters outside of the Avengers. This statement could also be a reaction to real - life changes in the official Marvel storylines, with the author adapting it to their fan - created stories.
Tony Stark may dislike Avengers fanfiction because it can mess with the emotional core of the team. The real relationships between the Avengers are deep and complex. Fanfiction might simplify or distort these relationships. For instance, his friendship with Steve Rogers has many layers, and fanfiction could make it into something that doesn't do justice to their real bond. Also, he's a man who values his privacy to an extent. Fanfiction might delve into his personal life in ways that he doesn't appreciate, making him feel exposed and misrepresented.
One possible reason could be a major disagreement. Maybe the Avengers made a decision that Tony strongly opposed, like a dangerous mission plan that he thought was too risky. For example, if they decided to team up with a morally ambiguous character without proper precautions. Another reason might be personal issues. Tony could be going through something in his personal life that makes him want to distance himself from the group, like dealing with the stress of his identity as Iron Man being public and feeling the Avengers draw too much unwanted attention.
In a fanfiction scenario, Tony Stark could be hurt emotionally. For example, if there's a rift in the Avengers team and some of his closest friends turn against him. This could lead to him isolating himself and getting into a downward spiral of self - doubt and pain, which is really interesting to explore in fanfiction.
One possible reason could be jealousy. Maybe Tony's intelligence and wealth made some Avengers feel inferior, and over time, that festered into betrayal. For example, if Tony developed a new technology that could potentially overshadow their own abilities, they might feel threatened.
It could also be due to emotional turmoil. Tony has lost a lot in his life, like his parents and some of his friends. In the fanfic, if he was faced with a situation that reminded him of those losses or if he had a falling - out with a close ally like Pepper or Rhodey, the emotional shock could be so great that he collapses. He's a man who often keeps his emotions bottled up, and when they finally break through, it could have a physical manifestation like a collapse.
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.
One possible reason could be his excessive exposure to the arc reactor technology. The energy from the arc reactor might have gradually altered his DNA over time, causing him to become something other than human.
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.
One possible reason could be that Shield has been corrupted from within. Maybe Tony discovers some dark secrets or unethical practices within Shield that make him believe it's a threat that needs to be eliminated. For example, if Shield was involved in illegal human experimentation or was secretly working with enemies of the state.