Koji Koda is also underrated. His ability to communicate with animals could be the center of some really heartwarming and adventurous fanfiction. For example, he could lead a mission where the heroes have to rely on the animals' help to defeat a villain who has a quirk that affects the environment in a way that only the animals can sense.
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.
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.
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.
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.
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.
Well, it really depends on the creativity of the fanfiction writers. However, some might find a character who combines the strength of a male hero with the grace of a female character quite interesting. For example, a character who has the physical power of All Might but also the agility and charm of a female character. Another could be a character based on Deku, but with a futanari twist, having both the determination of Deku and some unique feminine qualities that add new layers to their personality.
Katsuki Bakugo is also a common character. His explosive personality can be interestingly combined with the gamer concept. Maybe a gamer - like Bakugo who is always looking for the next 'level up' in terms of his quirk strength and hero status, constantly challenging others in a competitive, almost game - like way.
Well, obviously Mandalay herself is a main character. Then there could be her fellow heroes like Tiger. Students she mentors might also be main characters, like Kota who she has a connection to in the original story.
I think Icarus is the central figure in this fanfiction. But characters like Midoriya Izuku would also be important. Izuku's journey as a hero - in - training could be intertwined with Icarus'. Maybe they become friends or rivals. And villains from My Hero Academia, such as Tomura Shigaraki, could also be main characters. His evil plans might be affected by or target Icarus, adding more drama to the story.
Lala is often an underrated character in Black Lightning fanfiction. He has a complex backstory as a gang member turned metahuman. There's a lot of potential to explore his redemption arc or his struggle between his old life and his new powers. Another could be Inspector Henderson. He's often in the background but could be developed more. He could have his own investigations that cross paths with Black Lightning in interesting ways.