Harry might be shocked at first. He'd probably feel a sense of urgency to break the Imperius Curse. He could also feel a bit of pity for Draco, as Draco is being controlled against his will.
Harry would most likely react with a mix of emotions. Initially, there would be disbelief as it's a serious and dark magic situation. Then, his natural instinct to help those in trouble would kick in. He'd start observing Draco closely to figure out the best way to counter the Imperius Curse. He might also recall his own experiences with dark magic and use that knowledge to try and free Draco. At the same time, he'd be on guard in case Draco, while Imperiused, was made to do something harmful.
Well, in many such fanfictions, Harry might be shocked at first. He probably feels a sense of pity for Draco too. After all, being under the Imperius Curse means Draco has no control over his actions.
He might be shocked at first. Then he could feel a strong sense of protectiveness towards Harry. Maybe he immediately tries to find ways to keep Harry safe from further harm, like staying closer to him at all times.
Well, Bill could be shocked at first. But then he would likely become very protective. He may take Harry to a safe place, like the Burrow, and gather his family around to support Harry. He would also probably try to find out more about the abuse, like who was behind it and for how long it had been going on. He'd be determined to make sure it never happened again.
Sirius would likely be extremely angry. He already has a protective streak towards Harry. He might immediately confront those he suspects of the abuse, whether it's the Dursleys or others at Hogwarts. He would probably also try to remove Harry from the situation as quickly as possible.
Arthur might be shocked and immediately want to protect Harry. He could start by confronting those who are abusing Harry or find a safe place for Harry to stay.
Viktor might be shocked at first. He could feel a strong sense of protectiveness towards Harry. Maybe he immediately tries to comfort Harry and assure him that he's not alone anymore.
Well, Dumbledore has always had a special connection with Harry. When he finds out about the abuse, he would be devastated. His first instinct would be to comfort Harry. He might also reflect on his own actions and whether he could have prevented the abuse from happening. Dumbledore would then use all of his resources to make sure Harry is safe and happy. He could provide Harry with a mentor or a guide to help him through the difficult times, someone who can teach Harry how to cope with his past and move forward in a positive way.
Harry might be initially shocked. He could feel a mix of sadness and a sense of responsibility. After all, Sirius was like a father figure to him.
Harry is likely to be shocked at first. He has always seen Draco as a self - willed rival, so finding out that Draco is being controlled by the Imperious Curse completely changes his perception. He might freeze for a moment, trying to process what he has just realized.
Harry's reaction would be complex. He has been at odds with Draco for so long that this revelation completely changes the dynamic. He would likely experience a sense of disbelief that such a thing could be happening to Draco. As he processes it, he would start to feel empathy towards Draco. Harry might approach Draco cautiously at first, not sure how Draco would respond to his newfound knowledge. But he would be determined to help in some way, whether it's by using his influence in the wizarding world or just being there for Draco as a friend. This could also lead to a significant shift in the relationship between the Gryffindors and Slytherins as a whole, as Harry's actions towards Draco could inspire others to look at Slytherins in a different way, seeing that they too can be victims of difficult situations.