At first, Sans would probably be a bit shocked, but then he'd turn on his laid - back, sarcastic attitude. He might make jokes at Gaster's expense, which could either annoy Gaster or make him respect Sans more. If Gaster tries to harm him, Sans could use his shortcuts to dodge attacks and try to find a way to reverse the situation. He'd also likely be thinking about how this affects his friends in the Underground, especially Papyrus, and try to find a way back to them.
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.
Hermione may first try to use magic to defend herself or escape right when the kidnapping is taking place. But if that fails, she will start to analyze the situation. She would think about what she knows of Dolohov from her studies and any previous encounters. Then, she would form a plan. She might even try to find allies within Dolohov's ranks if there are any who could be swayed, by appealing to their sense of self - preservation or better nature.
Percy would likely be both angry and calculating. He'd be angry because he's been kidnapped, but he'd also start thinking about how he can use his powers and skills to get out of the situation. He might try to reason with Khione if he thinks it could buy him some time to plan an escape. He'd also be looking for any weaknesses in Khione's defenses or in her personality that he could exploit.
He could also be initially confused. Sasuke has known Sakura for a long time, and this unexpected act from her would leave him wondering about her motives. He may hold back his anger for a while to hear her out and understand why she did such a thing.
Naruto would probably be really angry at first. He's a free - spirited person who doesn't like being forced into things. So he'd likely try to fight back right away, yelling at Sasuke about what he's doing.
Axel would probably be extremely angry. He would likely immediately start looking for Kairi. He might go on a solo mission to find her, using all his skills and knowledge of Saix's possible hiding places.
She would most likely be furious. Hermione is a smart and independent character. She would immediately start planning her escape. She might use her knowledge of magic to try and outwit Draco.
At first, Bruce might be scared. He knows Loki's reputation for being unpredictable and dangerous. But he also tries to keep his cool because he doesn't want to accidentally transform into the Hulk right away. He might try to reason with Loki, using his intelligence to talk his way out of the situation.
Clarice could also become very defiant. She is a strong - willed character. So, instead of cowering, she might constantly challenge Hannibal, trying to get under his skin and make him make mistakes. This could lead to some intense mental battles between them within the fanfiction.
Elena would probably be terrified at first. She's a human in a world full of powerful supernatural beings. Being kidnapped by Damon would mean she's in a very vulnerable position. She might initially try to fight back or escape, using any opportunity that presents itself.