Ned Leeds could be a great character to focus on more. In the movies, he has been mostly a sidekick. But in fanfiction, we could explore his powers further. Maybe he discovers new abilities related to the magic he dabbled in, and he uses them to help Peter in ways that are unexpected. For example, he could develop the ability to create portals not just to other places on Earth, but also to different dimensions.
MJ is also an underrated character in this context. Fanfiction could explore her character more deeply. She could have her own arc where she becomes more involved in the superhero world. Maybe she starts training in self - defense or learns some skills that can help her and Peter in their fight against villains. She could also be the one to come up with unique strategies to deal with threats from the multiverse.
Rock Lee is often overlooked compared to the main characters. A fanfiction could focus on his journey to become an even greater ninja without relying on ninjutsu. Another underrated character is Shino Aburame. His unique bug - related abilities could be explored more deeply in a fanfiction, like how he might use them in different and unexpected ways.
The neighbor who was briefly shown in the movie could be an interesting character to focus on. We didn't really get to know much about him, but fanfiction could explore his story, like how he managed to survive on his own for so long. Maybe he had some unique skills or knowledge that helped him. Another could be the old man who we saw at the beginning. What was his life like before the invasion? Fanfiction could give him a more detailed backstory.
The old hermit character. He was only in a few scenes but seemed to know a lot. Fanfiction could explore his past and how he came to have his knowledge. There's also the young apprentice who was often overlooked. He might have some hidden powers or a special connection to the treasures that could be delved into.
One underrated character is Baltus Van Tassel. He's Katrina's father and has a big role in the town. Fanfiction could explore his backstory, like how he came to be such an important figure in Sleepy Hollow. Maybe he had some adventures in his youth that are related to the Horseman legend. Another is the schoolmaster before Ichabod Crane. What was his experience in Sleepy Hollow? What did he know about the Horseman that he might have passed on to Ichabod? And then there's the old woman who lives on the outskirts of town. She might seem like a minor character, but she could be a seer or have some connection to the supernatural forces in Sleepy Hollow.
Lyon Vastia could be a great character to focus on. He has powerful ice - make magic, but often gets overshadowed by Gray. In a GMG fanfiction, he could have his own moment to shine, perhaps by teaming up with Fairy Tail for a special event in the games.
Artemis is a character that could be explored more in fanfiction. She has a complex backstory and during the Invasion, she could be given more depth. For example, her relationships with other team members could be further developed, especially how she deals with the stress and danger of the invasion while also maintaining her cover if she still has one at that point.
One underrated character for Harry Potter OotP fanfiction is Seamus Finnigan. He had his own doubts about Harry in the original story. You could expand on that. What if he had a change of heart in a more in - depth way? Maybe he discovers something that makes him fully trust Harry again. Also, Parvati Patil could be a focus. She could have her own side story about her Divination skills and how they might play a role in the bigger battle against the Dark Lord.
Definitely Firenze. He made an appearance in this book, but in fanfiction, he could be more involved. Since he has unique insights as a centaur, he could play a key role in helping Harry understand the prophecies or the true nature of the events related to Sirius. Also, consider Madam Pomfrey. She's often overlooked, but she could be a great source of knowledge about past students and events at Hogwarts that might be relevant to the situation with Sirius.
Tenten. She doesn't get much spotlight during the war. A fanfiction could explore her role in providing weapons and support from behind the scenes. Maybe she invents a new type of weapon that could turn the tide of a small battle.
Kiba and Akamaru. They don't often get the spotlight during the big events like the Fourth War. In a fanfiction, they could have a special mission during the war. Maybe they discover a new type of enemy that can only be detected by Akamaru's sense of smell, and they have to use their teamwork to defeat it.