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.
Another plot twist might be that Loki is being controlled by a more powerful entity when he kidnaps Tony. This could add an extra layer of mystery and conflict. The Avengers might initially think Loki is acting on his own volition, but as they investigate, they discover that he is a puppet in someone else's scheme. And Tony, while kidnapped, tries to figure out a way to break Loki free from the control and in the process, they form an unlikely alliance.
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.
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 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 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.
One possible plot twist could be that Aizen has a hidden motive other than just causing chaos. Maybe he kidnaps Ichigo to use his unique powers for some sort of experiment. For example, he might want to extract the power of Ichigo's Hollow side to enhance his own strength or create a new type of Arrancar. Another twist could be that Aizen is being controlled by an even greater force, and Ichigo's kidnapping is part of a larger plan to draw out other powerful characters in the Soul Society.
Another aspect could be that the Kyuubi is being controlled by a hidden force when it kidnaps Naruto. This hidden force might be using the Kyuubi's power to start a war between the village and other hidden villages. They could be framing the Kyuubi to create chaos, and Naruto, being the jinchuriki, is the key piece in their evil plan. Naruto might then have to figure out a way to break free from the Kyuubi's hold and expose the real villains behind the kidnapping.
In a Toga kidnaps Midoriya fanfiction, the plot could go in various directions. Maybe Toga kidnaps Midoriya to trade him for something she wants from the heroes, like the release of a fellow villain. Midoriya, on the other hand, could try to escape by using his wits and his knowledge of Toga's weaknesses. For example, if he figures out that she has a soft spot for a certain type of person or situation, he could use that to his advantage. Also, the story could involve the other students at U.A. trying to rescue Midoriya. They might come up with a clever plan that involves using their individual quirks in a unique way to outsmart Toga and get Midoriya back.
Another idea is that the fanfiction could be a dark, alternate universe story where Jasper has turned evil. His reasons for kidnapping Bella could be tied to some sort of revenge plot against the Cullens. He might hold a grudge against them for something that happened in the past, and Bella is just a means to get back at them. This would create a very different dynamic compared to the original Twilight story.