Since I don't know the 'Back in Black Novel' well, it's hard to say exactly. But there could be a strong - willed protagonist who is at the center of the story, maybe someone who has a troubled past.
There might be a protagonist who is trying to reclaim their former glory or status. Alongside them, there could be a supporting character, perhaps a mentor - like figure who helps the main character navigate through the challenges they face in the 'back in black' situation. Or there could be an antagonist who is trying to prevent the protagonist from achieving their goal of getting 'back in black' in a positive sense, like regaining their power or reputation.
In the 'Back in Black' story, the main characters are the members of AC/DC. Angus Young with his iconic schoolboy look and his amazing guitar skills. Brian Johnson, who stepped in as the lead singer after Bon Scott's death and played a crucial role in making the 'Back in Black' album what it is.
Deadpool is obviously one of the main characters. Given his nature, he's likely to be the central focus. There may also be some other characters from the Marvel universe that he interacts with, like Cable or Domino, who often get involved in Deadpool's storylines.
Peter Parker, of course, is the main character. He's Spiderman. And there are also his loved ones like Mary Jane. Also, his enemies play important roles too.
Deadpool is obviously the main character. He's the one in the black suit driving the story forward with his antics.
Another possibility is that it could focus on some of the recurring characters from the show but give them a more prominent role. For instance, Castiel could be a main character in this fanfic, and the 'back in black' concept could be related to his journey or a new aspect of his powers.
There could also be a mentor - like character. Someone who has either been through a similar experience before or has some special knowledge that can help the protagonist in their journey through hell and back. For example, an old wise man or woman who gives crucial advice at key moments.
In 'the way back novel', the main characters could be a group of people. For example, a family might be on a collective journey back to their heritage or a place of significance. Each family member could have their own role, with one being the leader of the journey, another being the one who questions the whole idea, and others having different reactions to the events that unfold during the way back.
Since I don't know the specific 'back to life novel', I can't say for sure. But it could have a character who has come back to life as the main character, along with those who are affected by their return, like family members or friends.
Since I haven't read this book thoroughly, I can't name the exact main characters. However, they could be people from different walks of life. There could be a young, ambitious character trying to make a name for themselves, and an older, more established character who acts as a foil or a mentor in some way.
Doc Brown is another main character. He invents the time - traveling DeLorean. He is a brilliant but eccentric scientist. His wild ideas and inventions drive the story forward as he is the one who makes the time - travel possible for Marty.