Harry is the main one as it's his faked death. Hermione, with her sharp mind, would be a mainstay in the story. Ron, with his loyalty and bravery, would be right there. Neville could also be a main character. He has grown a lot throughout the series and could be involved in the events surrounding Harry's faked death, perhaps even being one of the first to suspect something fishy. And then there's Ginny. As Harry's love interest, she would be deeply affected by his faked death and would be a central figure in the emotional turmoil of the story.
For Ron and Hermione, they would likely be devastated at first, thinking they had lost their best friend. But then they might start to suspect something when they notice small details that don't add up. Ginny would be heartbroken and might become more determined to fight against Voldemort in revenge. The Order of the Phoenix would be in chaos, with some members losing hope while others might start to investigate the circumstances of his 'death' more closely.
There could be an antagonist in the fanfic. Maybe someone who had a vendetta against Harry Merchant and was somehow involved in his death. This character would add conflict to the story as the people left behind try to figure out what really happened to Harry.
Voldemort would remain a major character. Harry's new abilities and perspective from being raised by Death would make their conflict even more complex. Harry might approach the fight against Voldemort with a different strategy, one that is influenced by the teachings of Death.
In a lot of these fanfictions, Luna Lovegood can be a key character. She has an open - minded and unique way of looking at things. So she might be the one who first suspects that Harry isn't really dead, or she could be part of the plan to help Harry fake his death and then communicate with him in some secret way while everyone else thinks he's gone.
Harry could also be a key character. As Hermione's best friend, he would be highly suspicious of her death. He might start his own investigation, using his skills as a wizard and his knowledge of Hermione's habits and secrets. His actions could either help or hinder Hermione's plan, depending on how things unfold.
Obviously, Harry Potter himself. He's the one who has become the Master of Death. Hermione and Ron would also be important. They'd be there to support Harry, and also to question his new power and the moral implications. Dumbledore might also play a role, perhaps as a guide from beyond the grave, since he was always so interested in the Deathly Hallows and what it means to be the Master of Death.
Obviously, Harry Potter would be the main character since it's in his name. He is the one who befriends Death. Hermione Granger and Ron Weasley are also likely to be important characters. They are Harry's closest friends and would be involved in the story, either trying to understand Harry's new friendship with Death or being affected by it in some way. For example, they might be worried about Harry's sanity or the implications of befriending such an otherworldly being.
Well, aside from Harry and Death, his friends like Hermione and Ron could also be important characters. They might try to stop Harry from making the deal or help him fulfill the terms of the deal. There could also be some other magical creatures or beings that are associated with Death, such as the Grim Reaper - like figures in the wizarding world. And perhaps some powerful wizards or witches who have had past experiences with Death could also be part of the story.
Harry Potter would probably be one of the main characters. He's the central figure in the original series, so it's likely he'd be involved in this fanfic in some capacity, perhaps as the hitman or someone related to the hitman - style plot.
Obviously, Harry Potter himself would be one of the main characters. He's the hero of the original series and his story would likely continue in this fanfic.