Well, Dumbledore might be more understanding. He knows Snape has his own motives and might suspect that there's more to the kidnapping than meets the eye. He would try to talk to Snape first. The other teachers would be divided. Some would side with Harry and think Snape has gone too far, while others might wait for more information. The students would be in an uproar, especially those who are friends with the kidnapped person. They'd form groups to try and find out what happened and rescue their friend.
If Snape kidnapped someone in fanfiction, the Order of the Phoenix would be on high alert. They'd see it as a sign that something big was about to happen. Sirius, if he were still alive, would be furious and would want to go after Snape immediately. Lupin would be more cautious, trying to figure out Snape's reasoning. Ginny would be worried about the kidnapped person and would use her own skills and connections to try and find them. Neville would be scared but also determined to help, as he's grown braver throughout the series.
At the beginning, Harry would be frightened. He's in an unknown place with Loki, who is known for his trickery. But Harry is no pushover. He would quickly gather his courage. He would remember all the times he's faced danger at Hogwarts. He might try to communicate with Loki to understand his motives. If Loki reveals that he wants to use Harry's magic for something, Harry would try to find a way to outsmart Loki. He could pretend to cooperate while actually looking for a weakness in Loki's plan. Harry would also be thinking about his friends at Hogwarts and how he needs to get back to them, which would give him extra motivation to fight back against Loki.
Snape would probably be very conflicted. On one hand, he has a long - standing grudge against James Potter, Harry's father. But on the other hand, he loved Harry's mother, Lily. So, he might be cold at first, but then his sense of protecting Lily's son could kick in. He would likely be very strict with Harry, as he is with all his students, but also secretly keep an eye on him to make sure he's safe.
Hermione would be extremely worried and would start researching like crazy to find out where Dumbledore has taken Harry. She would probably suspect that something is not right with Dumbledore and would try to convince Ron to help her. Ron, on the other hand, would be initially shocked but then would be ready to go on a rescue mission with Hermione.
The students would have a wide range of reactions. The Gryffindors might be more vocal about their surprise, with some being more accepting than others. The Slytherins would be more divided. Some of Snape's loyal Slytherin students might be protective of him, regardless of his new form, while others might see it as a sign of weakness. Draco Malfoy would probably be initially disgusted but as he sees Snape still maintaining his authority, he might change his attitude. And the Hufflepuffs would generally be more kind - hearted and accepting, perhaps offering Snape small tokens of support like homemade treats or kind notes to help him through this difficult change.
Snape would likely be angry at first. Harry has always been a source of trouble in his eyes, and running away would just add to that perception. He might mutter some sarcastic remarks under his breath about Potter's irresponsibility.
Harry would probably be quite resentful at first. He might think Snape is just being his usual unfair self. So, he would be sulky and do the tasks reluctantly.
He'd probably be annoyed. Snape is a serious wizard and he might think fanfiction is a silly Muggle - influenced concept.
Snape would likely be initially suspicious. He's not used to Harry coming to him for help or sharing secrets. But once he realizes the seriousness of what Harry is saying, he might start to see Harry in a new light. He could be grudgingly helpful, still maintaining his cold exterior but secretly starting to feel a bit more protective of Harry.
The Slytherin house would probably be outraged. Snape is one of their own, in a sense. They would demand justice for Snape and might even use this incident to fuel their long - standing rivalry with Gryffindor. There would be a lot of tension and conflict within the Hogwarts community as a result of this act.
The Order of the Phoenix would immediately spring into action. They would start searching for Harry using all their magical resources, including spells like the Tracking Charm. Dumbledore would likely be at the forefront, using his vast knowledge and connections to try and figure out where Loki has taken Harry.