Sato Rikido is an underrated character. In a fanfiction set during a baking competition at U.A. (as he loves baking), his skills and how his quirk might give him an edge could be explored. Also, Koda Koji, who can communicate with animals. A story about him during a period when the school is facing an animal - related problem would be interesting. It could show his importance and how he uses his quirk to solve the issue.
Tsuyu Asui is often overlooked. She has a really cool quirk with her frog - like abilities. In fanfiction, she could be the main character in a story about amphibious hero training or exploring the swamps and water - based areas that other heroes might avoid.
Hagakure. She's often overlooked because she's invisible, but she could be the star of a really fun fanfiction. Maybe a story where she uses her invisibility in really creative ways to solve mysteries around UA or prank her classmates.
Juzo Honenuki is a great choice. His Softening quirk has a lot of potential for interesting storylines. He could be in a situation where he has to use his quirk in a creative way to save his classmates from a collapsing building or something similar.
Mezo Shoji is another one. His multiple - armed quirk could be used in so many creative ways in fanfiction, but he's not often the main character. There could be stories where he uses his arms not just for combat, but also for things like creating elaborate structures or helping in rescue operations in a unique way that other characters can't.
Definitely Deku. His journey from being quirkless to one of the most powerful heroes - in - training is inspiring. You can explore more of his self - doubts and how he overcomes them in different scenarios. Bakugo is also a popular choice. His explosive personality and powerful quirk make for great storylines, especially exploring his relationship with Deku further. Uraraka is another great character. Her gravity - defying quirk can be used in unique ways in fanfiction, like in rescue missions or in battles against villains with flying abilities.
Stain could be considered as an anti - hero in fanfiction. His extreme views on heroes, while not entirely acceptable, could be delved into deeper. He believes that only true heroes should be recognized and is willing to take extreme measures to prove his point. A fanfiction could explore a different side of him, perhaps one where his actions are more nuanced.
The Wasp. She is a powerful and intelligent character. A fanfiction could center around her leadership skills within the Avengers. Maybe she has to lead the team in a situation where all the big - name heroes are incapacitated. It would show her strategic thinking and her ability to inspire others.
The stable hands who take care of the dragons often get overlooked. They have a unique perspective as they interact closely with the dragons on a daily basis. Fanfiction could explore their lives, their dreams, and how they view the dragon riders.
The White Rabbit is often just seen as the one who leads Alice into Wonderland, but he could be so much more in fanfiction. He could be a time - traveler, for example, and his hurry is because he's always on a tight schedule to different eras. The Tweedle brothers are also underrated. They could be the key to unlocking some ancient secrets of Wonderland. In a fanfiction, they could lead Alice on an adventure full of riddles and puzzles that reveal the true nature of Wonderland. And the Caterpillar is quite an interesting character to focus on. It could be a wise sage who holds the knowledge of the entire Wonderland universe.
Shino Aburame is quite underrated. In a fanfiction, he could be shown as a key figure during the Revolution. His unique insect - based jutsu could be developed further, and his calm and intelligent nature could be used to his advantage in the political and social upheaval of the time.