One way is to put Genos in a situation where he's outnumbered. As the enemies attack him from all sides, his defenses are slowly broken down. The writer can describe the attacks hitting him one by one, each causing more damage. They can also make the reader feel Genos' desperation as he realizes he might not be able to survive this time. And then, there's the aftermath. How does he deal with the pain and the damage? Does he become more determined or does he start to doubt himself? These are all aspects that can make a hurt scene for Genos impactful in a fanfiction.
In some fanfictions, Genos could be hurt by a villain who targets his emotional side. The villain might find out about Genos' past, his desire to become stronger, and use that against him. They could manipulate his memories and make him experience the pain of his past all over again, which causes his mental state to deteriorate and also affects his physical functions as his mind and body are connected.
Genos is still kicking in the One Punch Man manga. The author has managed to keep him in the storyline without killing him off. There's always the possibility in the future, but for now, he's alive and fighting.
Female Genos could be developed with a more empathetic side. Since she is a cyborg, she could struggle with understanding human emotions more deeply. Maybe she starts to learn about love and friendship in a different way compared to male Genos. For example, she might be more sensitive to the feelings of other female characters around her.
One interesting fanfiction storyline could be that Genos discovers a prophecy that Saitama is going to lose his powers. Genos then goes on a mad quest to find a way to prevent this from happening. He visits all kinds of strange places and consults with various powerful beings. Another could be that there is a competition among heroes to see who can train the best new recruit, and Saitama and Genos enter together. They face off against other hero - trainer pairs in various challenges. Also, a story where Genos creates a virtual reality world for Saitama to experience different kinds of battles that he normally wouldn't encounter in the real world, just for Saitama's amusement.
A great storyline could involve female Genos exploring her new - found femininity while still maintaining her badass fighting skills. Maybe she gets invited to a hero - only fashion event and has to figure out how to balance looking glamorous and being ready to fight any villains that might show up. Or perhaps she teams up with other female heroes to form an all - female hero squad and they take on a super - powerful male villain who underestimates them.
Well, Genos in One Punch Man has a very interesting story. He was once an ordinary human but after the tragic event of his hometown being destroyed, he decided to turn himself into a cyborg. He's highly dedicated to his training under Saitama. He often gets into battles with various monsters, always aiming to prove himself and grow stronger. His character also shows a great deal of loyalty to Saitama and the cause of protecting the city from threats.