Bruce would probably be more analytical. He might wonder how Tony's marriage could affect his work and the team. He could also be curious about Tony's relationship dynamics. Meanwhile, Wanda might sense the emotions involved, like Tony's happiness or any underlying stress in the relationship. And Rhodey would likely be supportive, since he's Tony's close friend. He might even help Tony deal with any potential issues that come up with the Avengers' reactions.
Thor could be angry. He's a proud warrior and being kicked out like that might be seen as an insult. He might even challenge Tony in some way, either verbally or physically. However, he also has a sense of honor and might listen to Tony's reasons if given the chance.
If the hurt is physical, Tony could retaliate in self - defense. He has his Iron Man suits, which he could use to protect himself while still trying to avoid causing too much harm to his former friends. At the same time, he would be deeply hurt emotionally and might start to question his relationships with the Avengers.
They might be in shock. Tony has a complex past, and seeing it all unfold could leave them speechless.
Peter is likely to be in awe. He might be a bit nervous at first, but also extremely excited. He has looked up to the Avengers for a long time, so meeting them would be like a dream come true. He would probably be stuttering a bit as he tries to introduce himself and show his respect.
The Avengers may become more empathetic. Learning about Tony's family issues or his unspoken fears through fanfiction could make them understand his sometimes difficult behavior better. They might start to cut him some slack when he acts brashly, realizing there are underlying reasons for it.
The Avengers would be in a state of panic and fury. Captain America would likely lead the charge to find Tony. He'd use his military strategy skills to plan a rescue mission. Thor might use his godly powers to track down any signs of Tony's whereabouts. Black Widow and Hawkeye would be on the lookout for any Hydra agents or informants. Hulk could be a wildcard. He might be uncontrollably angry and ready to smash anything in his path to get to Tony.
They would react differently. Tony might be a bit embarrassed but also secretly pleased. The others, like Thor, would probably be very curious and want to read some of it.
Tony would probably be extremely hurt. He trusted his team, and betrayal would cut deep. He might initially be in denial, not wanting to believe that his friends could turn on him.
Some Avengers might be initially shocked. For example, Steve could be a bit taken aback as he tries to understand how this could be possible. He might be concerned about the implications for the team dynamics.
The Avengers finding out Tony is married in fanfiction could create a whole new set of storylines. For example, if Tony's marriage was a result of some kind of arranged situation, the Avengers might get involved in trying to figure out if it's a good or bad thing for Tony. Or if his spouse has a hidden power or identity, it could bring danger to the team, and they'd have to deal with that. There could also be relationship drama within the team, like jealousy from a character who has an unrequited love for Tony. This discovery could be a catalyst for many different plot twists and character developments.