The relationship could be depicted as a reluctant partnership. Maybe they are forced to work together to solve a mystery that involves werewolf lore and some ancient magic. Hermione is initially disgusted by Fenrir but as they spend more time together, she discovers that he has a tragic past that led to his current state. Fenrir, on the other hand, respects Hermione's power and intelligence. This mutual discovery forms a complex and unique bond between them.
A very different way to show their relationship is if they are both trapped in a magical realm together. In this realm, they have to rely on each other to survive. Hermione uses her intelligence to solve the puzzles of the realm, and Greyback uses his werewolf instincts. As they work together, they start to respect each other. Greyback realizes that Hermione is not just a weak Muggle - born, but a powerful witch, and Hermione sees that Greyback has a side to him that is more than just a blood - thirsty beast. This shared experience could create a bond between them that is both unexpected and complex.
In some fanfictions, the relationship is portrayed as one of pure enmity. Fenrir Greyback, being a cruel and savage werewolf, is seen as a threat to Hermione. He represents the dark and violent side of the wizarding world that she is constantly fighting against. His predatory nature towards her, especially given her Muggle - born status, makes for a very tense and hostile relationship.
Their relationship could start with Hermione being a captive of Fenrir. But instead of harming her immediately, he becomes intrigued by her intelligence. As time passes, Hermione might start to see some humanity in Fenrir that others don't, and they could form an unlikely alliance against a common enemy.
Their relationship could start with Hermione being cautious. She might initially see Fenrir as a threat despite his 'good' nature. But as she gets to know him better, she realizes his potential for good. They could start working together on small projects, like helping other werewolves in the community, which gradually builds trust between them.
Their relationship might develop through a series of tense encounters. Fenrir might be initially attracted to Hermione's magic and her strong will. As they interact more, Hermione could start to see a glimmer of humanity in Fenrir, despite his monstrous actions. This could lead to a complex relationship where she tries to reform him in some way, while he struggles with his dark nature and his growing feelings for her.
Perhaps it's the allure of the 'forbidden'. Fenrir Greyback is a dark and dangerous character, and exploring his relationship with Hermione in fanfiction might be an exploration of the contrast between light (Hermione) and dark (Greyback).
In one fanfiction concept, Greyback saves Hermione when she is trapped in a magical maze created by dark wizards. Greyback, being a cunning and experienced dark creature, is able to navigate the maze and get to Hermione before the maze collapses or she is killed by the various traps inside. He might save her because he senses that she has a great potential that could be useful to him in the future.
There's a fanfiction called 'Greyback's Redemption Arc'. In it, Fenrir Greyback saves Hermione from a group of Death Eaters. The author might have written it to explore the idea of redemption for a character like Greyback. Maybe he saves Hermione because he sees her as a symbol of the good in the wizarding world that he has lost touch with, and this act of saving her could be the start of his journey towards redemption.
Authors often portray it as a very antagonistic relationship. Fenrir is a dark and violent character, and Hermione is a symbol of good and knowledge. So, their interactions are usually filled with tension, like Fenrir seeing Hermione as a target because of her connection to Harry Potter and the fight against Voldemort.
Their relationship could develop as a sort of teacher - student dynamic in a way. Fenrir has a lot of knowledge about the dark side of the wizarding world that Hermione doesn't. He could share some of that knowledge with her, while Hermione could teach him about the values of the good side, like compassion and equality. Over time, they could form an unlikely friendship based on mutual learning.