Brennan and Booth are obvious choices. Their relationship is at the core of the show, so exploring different aspects of it in fanfiction can be really interesting. You can dig deeper into their pasts, like Brennan's childhood traumas and how that affects her relationship with Booth, or Booth's military experiences and how they shape his views on love and commitment.
Sweets is another character worthy of focus. His psychological insights into Brennan and Booth's relationship can be the center of a fanfiction. For example, a story where Sweets writes a book about their relationship based on his observations, but it causes some unexpected drama between Brennan and Booth. And Cam can also be focused on, like a fanfiction about her leadership style and how she manages the team during difficult cases.
Angela is also a great character to focus on. She's Brennan's best friend and has her own unique perspective. A fanfiction could be written about Angela's role in helping Brennan through her relationship problems with Booth. Also, Hodgins is interesting. His love for bugs and his relationship with Angela can be explored more in fanfiction. Maybe a story about how he balances his scientific passion with his love life.
I'm not entirely sure without reading it, but it might feature characters similar to those in the Bones series, like Temperance Brennan and Seeley Booth. They could be the main focus, with their relationship and their work as forensic anthropologists being central to the story.
I think focusing on Ruby and Weiss would be good. Ruby as the leader has so many aspects to explore, like her insecurities and how she overcomes them. Weiss, on the other hand, has her own journey of breaking free from her family's expectations. They also have a great dynamic together, which can be developed further in the fanfic. But Blake and Yang are also important, especially if you want to show their friendship and how they support each other through tough times.
Jace is another favorite. His complex personality, with his cocky exterior but deep - seated insecurities, makes him an interesting character to write about. Fanfictions might explore his past more deeply, like his relationship with Valentine, and how that shapes the person he is in the present. Also, his romantic relationship with Clary is a common theme to expand on in fanfiction.
The main family members can be great to focus on. Their relationships, power struggles, and dreams offer a lot of material. For example, the patriarch of the family who has to make tough decisions to keep the ranch going. Another good character could be the strong - willed matriarch who holds the family together. Also, the young and rebellious heir who wants to do things his own way.
Definitely Atreyu. His backstory, like his training and family, can be delved into deeply. You can also explore his emotions during his quest, like his fear and his hope. Then there's Gmork. Writing about his motives and his past could be fascinating. Maybe he wasn't always evil. And the Empress? She has so much power and mystery. Fanfiction about her early days on the throne or her relationship with the different beings of Fantasia would be very engaging.
Gardner Elliot is often a popular choice. His unique situation of being born on Mars and coming to Earth gives a lot of room for exploration in fanfiction. Writers can delve into his experiences adjusting to Earth, his relationships with other characters from different perspectives.
Definitely Bigby. His past as the Big Bad Wolf and his struggle to be something more in Fabletown is fascinating. He has so many relationships to explore, like with Beauty and Beast, and how they view his role. Another great character is Bluebeard. He's a bit of a villain, but that makes him interesting. You can write about his schemes and how Bigby tries to stop him. Also, the Crooked Man is a character that can be the center of a great fanfiction. Unraveling his mystery and how he's been manipulating things in Fabletown can be really engaging.
Sersi is a great character to focus on. She has a strong connection to humanity and her powers are quite interesting. You could explore her relationships with humans in more detail. Another good one is Ikaris. His loyalty and the internal conflict he might face are good material for a fanfiction. Then there's Kingo, with his love for movies and his unique charm among the Eternals.
All of the members of 4 town are great to focus on in different ways. Tae Young, for example, might be the subject of a fanfiction where his amazing dancing skills are the center of the story. Maybe he gets an offer to be in a big dance competition outside of the band, and he has to decide whether to take it or stay loyal to 4 town. Each member brings their own unique traits that can be explored in fanfiction.
For me, Choi Nam - ra is an underrated character for fanfiction. We could write about her internal struggle with the virus inside her in more detail. How does she really feel about the changes in her body? What if she tried to find a way to reverse it on her own? Also, Lee Su - hyeok could be the focus. A fanfiction could be about his relationship with other survivors in a more in - depth way, like how he helps them deal with their traumas during the apocalypse.