You can start by looking on popular fanfiction websites such as Archive of Our Own (AO3). AO3 has a vast collection of fanfictions from various fandoms, and there's a good chance you'll find some Hermione Granger x Fenrir Greyback stories there. Just use the search function and type in the relevant tags.
Fanfiction.net is another place to search. It has been around for a long time and has a large number of Harry Potter - related fanfictions. However, the tagging system might not be as refined as AO3. So, you may need to do a bit more sifting through the results to find exactly what you're looking for.
Some Tumblr blogs are also dedicated to sharing and discussing fanfictions. You could search for relevant tags like 'Hermione Granger x Fenrir Greyback fanfiction' on Tumblr. There might be users who have either written such stories or know where to find them. They might also provide some reviews or summaries which can help you decide if the fanfiction is worth reading.
The contrast between the two characters. Hermione is a brilliant, studious witch, while Fenrir is a savage werewolf. This contrast can lead to some really interesting character dynamics in fanfictions.
There could also be a fanfiction where Hermione Granger is forced to face Fenrir Greyback alone in a dangerous situation. This would showcase her bravery and her ability to use her magic skills under extreme pressure. The story could focus on her mental and magical struggle against Greyback, perhaps with her using some of the more advanced spells she has learned over the years to defend herself and those around her from the werewolf's attacks.
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.
One interesting storyline could be Hermione using her intelligence to outwit Fenrir Greyback. For example, she could create a spell or potion that repels werewolves like him. Another could be a scenario where Fenrir tries to capture Hermione for some dark purpose, but she manages to turn the tables on him with the help of her friends. Maybe she could also find a way to cure Fenrir's lycanthropy, leading to a change in his character.
One interesting plot could be Hermione trying to use her intelligence to outwit Fenrir Greyback. Maybe she's on a mission to rescue someone he's captured, and she has to use her magic skills in new and creative ways. For example, she could use a combination of transfiguration and charms to create distractions while she sneaks around his lair.
For Hermione, her development could involve facing her fears of werewolves like Fenrir. She might start off being very cautious and perhaps a bit prejudiced due to his reputation. But as the story progresses, she could learn to look beyond the surface and see the complex person (or creature) that Fenrir is. This would show her growth in empathy and open - mindedness.
I'm not sure if there is such a specific fanfiction. It seems like a rather dark and unusual pairing considering Fenrir Greyback is a werewolf known for his brutality. However, the world of fanfiction is vast, and there might be some out there that explore this concept, but it's not a common or mainstream idea in the Harry Potter fanfiction community.
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.
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.