Well, one plot twist could be that Yassen is actually working for Alex's father all along and the kidnapping is a test for Alex to become a better spy. Another could be that Yassen kidnaps Alex but then realizes Alex has information that could save Yassen's own family, so they form an unexpected alliance. Or perhaps Yassen kidnaps Alex thinking he's someone else, and when he discovers the truth, he has to figure out what to do with this innocent boy in his custody.
A possible plot twist is that Yassen is being controlled by a powerful and evil organization when he kidnaps Alex. But during the time of holding Alex captive, Alex manages to break through Yassen's mental control and make him see the truth. Also, it could be that Yassen kidnaps Alex to use him as a bait to draw out a mutual enemy, but in the process, Alex turns the tables and uses Yassen to get closer to that enemy himself.
Maybe Yassen kidnaps Alex with the intention of trading him for something valuable. However, as time passes, he starts to develop a strange bond with Alex. He discovers that Alex has a unique skill or knowledge that could change his own fate. So instead of trading Alex, he decides to protect him from the other parties who are also after Alex for their own malicious purposes.
Alex would probably be both scared and defiant at first. He's a brave kid, so he'd likely try to find a way to escape right away. He might also try to talk his way out, using his intelligence to reason with Yassen.
One possible plot could be that Yassen kidnaps Alex Rider to use him as a bargaining chip against MI6. Maybe he wants some secret files or information in exchange for Alex's safe return.
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 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.
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.
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.
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.
One possible plot twist could be that Drago kidnaps Hiccup to use him as a bargaining chip against the dragons. Maybe he wants to force the dragons to submit to his will by threatening Hiccup's life. Another could be that Drago discovers some special power within Hiccup that he wants to harness for his own evil purposes. For example, Hiccup's ability to communicate with dragons might be something Drago wants to use to control all dragons.
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 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.