His friends would be devastated. Hermione might be in deep shock and disbelief, constantly trying to find evidence that he's still alive. Ron would probably be angry and determined to find out what really happened.
In fanfiction, Harry could be believed to be dead for various reasons. It might be due to a powerful dark magic attack that seemed to extinguish his life force. Maybe he sacrificed himself to save others, like in many heroic tales. Or it could be a ruse created by him to deceive his enemies.
Hermione would probably be shocked at first. But then she would try to find a way to help Harry through it, using her vast knowledge of magic to figure out what's going on.
One common theme is the exploration of grief. Characters like Hermione and Ron go through intense emotional turmoil as they believe they've lost their best friend. Another theme is the revelation of hidden secrets. Often, as the story progresses, we find out that there were reasons behind Harry's faked death, like a secret mission or a plot to deceive the enemy.
Hermione would be extremely shocked and worried for Harry. She would see it as a dangerous situation and would try to find a way to break the contract through research. Ron would probably be more vocal about his disbelief and might even make some jokes about it at first, but then he'd also be concerned for Harry's safety. Dumbledore, being the wise figure, would see it as an opportunity to gain an edge over Voldemort. He would try to guide Harry on how to handle Bellatrix while being in this contract situation.
Hermione would probably be devastated. She was Harry's closest friend and ally. She might be filled with rage towards Vernon and vow to seek justice. Ron would also be heartbroken and might want to take matters into his own hands against Vernon.
One such fanfic could be 'The Aftermath of Harry's Faked Death'. In this fic, the wizarding world is in chaos after believing Harry is dead. It shows how his friends deal with the grief and how they start to uncover the truth that Harry might still be alive. It's a great read for those who like a bit of mystery and drama in their fanfics.
Ron would be furious. He's been friends with both Harry and Hermione for so long and has had his own unspoken feelings for Hermione. His reaction could range from shouting at Harry to giving them both the cold shoulder for a while.
Dumbledore's reaction could be complex. He might feel guilty for not realizing it sooner. In some fanfictions, he would try to make amends by providing more support and protection to Harry. Other teachers at Hogwarts, like McGonagall, would be sympathetic and might offer their own forms of help, like extra tutoring or a place for Harry to relax.
Hermione would probably be very angry and start researching ways to help Harry legally in the wizarding world. Ron, on the other hand, would be ready to fight anyone who had hurt Harry.
The characters from Leverage would be shocked at first. Eliot would probably be on high alert, ready to fight off any walkers immediately. Hardison would be freaking out a bit while also trying to figure out how to use his tech skills in this new world. Parker would be intrigued by the new environment full of challenges for her thieving skills. Meanwhile, the characters from The Walking Dead might be skeptical of the Leverage team at first, but would soon see the value in their skills as they start to help out.