Natasha could also experience a sense of sadness and hurt beneath her anger. She may have considered Percy a friend or ally, and the betrayal would make her question her judgment in trusting people. This could lead to her becoming more guarded and less trusting in future interactions within the fanfiction world.
She would likely become angry. Natasha is a strong character, and being betrayed would stir up her fury. She might start planning her revenge, using her skills and intelligence to get back at Percy. Maybe she'll try to expose his true motives to others in their world or group.
Natasha could also be disappointed but determined. She might see this as a setback but use it as motivation to prove herself elsewhere. For example, she could go and work for one of Tony's competitors and become very successful there, just to show Tony what he missed out on. She could also try to improve her skills or image to make herself more appealing in the future.
Then, she would probably be angry. Annabeth is a strong - willed character. She would feel betrayed and used, and her anger would fuel her to find out the truth. She might start her own investigation to figure out what's really going on with Percy, whether he's been influenced by someone or if there's another reason for his actions.
It could be a new villain that we haven't seen in the original Marvel universe. This villain might be able to manipulate Natasha's emotions and loyalty, making her betray Tony. For example, a powerful sorcerer who uses dark magic to control her.
Maybe in the fanfiction, Natasha betrays Tony because she has been brainwashed by an enemy organization. They manipulate her mind to turn against Tony and his Avengers team. This could lead to a lot of action and drama as Tony tries to figure out what's wrong with her and how to save her.
Natasha would likely be cautious at first. She has seen a lot in her life and new powers can be dangerous. But she would also be curious and protective.
Percy's reaction could also be one of self - doubt. He may start to question his own actions and leadership. He might think that he has done something wrong to push Annabeth away. However, his loyalty to his friends and the cause would eventually make him stand up against Kronos and try to bring Annabeth back to the right side.
Peter could also be a bit annoyed if it's not a good time. For example, if he was really focused on a test or a lesson he was interested in. But still, he'd probably answer because he knows Natasha wouldn't call without a good reason. He might give her a look that says 'this better be important' while trying to listen to what she has to say.
She becomes more nurturing. In most of these fanfictions, Natasha, who is usually seen as a tough spy and fighter, softens up. For example, she starts to cook for Peter, something she might not have done before.
She might try to manipulate Loki. Natasha is very good at getting into people's heads. She could play on Loki's ego or his own insecurities to gain an advantage. For example, she could pretend to be interested in his plans or offer to help him in some way, all while secretly planning her escape.
Another idea is that Percy gets thrown into the Marvel universe and Natasha is the first one to find him. She initially thinks he's some kind of new super - powered threat but soon realizes he's from a different realm. They then have to figure out how to get Percy back home while also dealing with the various threats that are attracted to Percy's presence in the Marvel universe.