Max is a no - brainer. Her character has so many layers, especially in the aftermath. She's dealing with the consequences of her time - traveling, which not only affected her but also the entire town. Chloe is also very interesting. She has a strong personality and her relationship with Max is central. You could also look at Rachel Amber. Even though she was a big part of the story before, in the aftermath, there could be more to discover about her. Maybe there are some secrets that are still hidden and the characters start to uncover them, which could be a really exciting plot point for a fanfic.
I think Max and Chloe are the top choices. Max has so much to deal with post - game. Her powers, her decisions, and how they affected everyone around her. She's constantly evolving and trying to understand herself. Chloe, on the other hand, has been through so much trauma. Her relationship with Max is also a key factor. You can explore how they support each other or maybe face new conflicts. But also, Victoria could be an interesting character to focus on. She was a bit of a bully in the game, but in the aftermath, she could have a redemption arc or struggle with her own insecurities.