Another plot twist could be that the reader has some sort of power or knowledge that Loki needs. So, instead of a malicious kidnapping, it's more of a strategic move on Loki's part. He might be trying to bargain with the reader to get what he wants, but as time passes, he starts to develop feelings for the reader.
One possible plot twist could be that Loki actually has a noble reason for kidnapping Tony. Maybe he wants to use Tony's intelligence to stop a greater threat that the other Avengers are unaware of. For example, there could be a hidden enemy that Loki has knowledge about, and he believes only Tony can help create a device or strategy to defeat it.
In this fanfiction, it could be that Loki was misled into thinking the girl was an enemy spy. So, he kidnaps her to interrogate her. However, during the interrogation, he discovers she's completely innocent. Now, he has to figure out how to make up for his mistake without losing his pride, and also deal with the potential chaos that his hasty action has caused among her friends and family.
Well, perhaps the plot of the fanfiction where Sasuke kidnaps the reader could involve a misunderstanding. Sasuke might think the reader is working for his enemies when in fact they are not. As for the story development, it could lead to the reader gradually understanding Sasuke's past traumas and reasons for his actions, and in the end, they might even help him heal some of his emotional wounds. And there could be a lot of action scenes where the reader tries to escape but then realizes that Sasuke is not really a bad guy in this situation.
In some cases, the reader could be in a state of shock and disbelief. They might not believe that this is really happening. But as they come to terms with the situation, they could start to form a plan. Maybe they try to appeal to Loki's better nature, if they believe he has one, by talking about his past actions and relationships that show his capacity for good.
One common plot twist could be that the reader turns out to have a hidden power or connection. For example, they might be related to a powerful figure in the Marvel universe. Another twist could be that Bucky has been brainwashed by an unseen force to kidnap the reader, and as the story unfolds, he starts to fight against that control. Also, the reader might find out that Bucky's kidnapping was actually a misdirected attempt to protect them from a greater threat that he knows about but the reader doesn't.
Well, perhaps Loki kidnaps the Hulk to use his strength in some scheme against the Avengers. Maybe he wants to use the Hulk to break into a secure location or as a weapon against Thor.
One possible plot could be that Loki kidnaps Natasha to use her as a bargaining chip against the Avengers. He might think that her skills and the Avengers' attachment to her would make them more likely to give in to his demands.
One possible scenario in this fanfiction could be that Loki disguises himself and lures Spiderman into a trap. He then transports him to a different realm where Spiderman is completely out of his element. Spiderman would have to rely on his wits and basic powers to try and escape Loki's clutches.
One possible plot twist could be that Pitch kidnaps Elsa not for his own gain directly, but to use her as a bargaining chip with the other guardians. For example, he might demand that the guardians give up their powers in exchange for Elsa's safe return. Another twist could be that Elsa discovers a new power within herself while being held captive by Pitch. Maybe her fear and the dark environment somehow unlock a power that is related to shadow or ice in a new way. And a third idea is that Pitch kidnaps Elsa because he realizes that her powers are a key to unlocking a greater power source that he wants to control, but Elsa manages to resist his attempts to use her in that way.
Well, in a Dracula kidnaps Mina fanfiction, it could go like this. Mina's friends might think she's dead at first. But then they start to notice strange things around town, like an increase in bat activity. They realize Dracula has taken her. Meanwhile, Mina could be trying to outwit Dracula by pretending to be on his side. She could slowly gain his trust and then find a way to escape when he least expects it.