Well, it might be good because it could have an interesting take on the characters of Hermione and Fenrir. Maybe it explores their relationship in a unique way that we haven't seen before in the original works.
Sorry, I'm not really sure of any specific ones similar to it off the top of my head. But you could try searching on fanfiction platforms using tags related to Hermione, Fenrir, and the genre of the original story it's based on.
In many such fanfictions, Hermione might start by trying to understand Fenrir's situation from a research perspective. She could be using her extensive knowledge of magic and werewolves to figure out a way to help him. For example, she might look into any spells or potions that could ease his lycanthropy symptoms.
There might be some out there, but it's a rather unusual pairing considering Fenrir Greyback is a werewolf with dark tendencies in the Harry Potter universe and Hermione is a heroic and intelligent witch. However, some fanfiction writers like to explore unique and 'what - if' scenarios. You could start by looking on popular fanfiction websites like Archive of Our Own or Fanfiction.net.
At the start, Hermione would be appalled by Fenrir's cruelty. She would be enraged that he has caused so much harm to innocent people. But as she delves deeper into getting to know him, she would start to see the complex web of factors that contributed to his behavior. She might see the neglect and discrimination he faced as a werewolf, which could make her feel a bit of pity. However, she would still firmly oppose his cruel actions and try to find a way to either contain or reform him, all while being acutely aware of the danger he poses.
Another theme is the idea of redemption. Many fanfictions explore whether Fenrir can be redeemed through his interactions with Hermione. It's about whether love or friendship can change a character who has been on the wrong path for so long.
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).
Fenrir might be intrigued by Hermione fanfiction because Hermione is a very intelligent and powerful character. Fanfictions often explore her potential in new and exciting ways, like her delving into different branches of magic or having unique adventures. This would be interesting to Fenrir as he may be curious about how she uses her wits and magic in these alternate scenarios.
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.