Perhaps there could be a time - travel aspect where Hermione goes back in time and has to deal with a younger Fenrir Greyback. She could try to prevent him from becoming the monster he is known to be in the future. This would require her to understand the root causes of his hatred and violence and try to change his path. It would be a very challenging task for Hermione as she would be dealing with a very different time period and set of values.
Another plot could be set in a world where Fenrir was captured and Hermione is tasked with trying to rehabilitate him. She could use her knowledge and magic to try and find a cure for his lycanthropy or at least control his werewolf side. This would involve a lot of study on Hermione's part and a lot of resistance from Fenrir at first.
One idea could be that Fenrir Greyback, instead of being a full - on villain, has some sort of complex relationship with Hermione. Maybe he's forced to protect her in a situation where they are both in danger from a greater dark force. This could lead to a lot of tension and moral dilemmas for Hermione as she has to deal with being around a werewolf who has a reputation for being cruel.
A possible plot is that Hermione, in her pursuit of equal rights for magical creatures, decides to reach out to Fenrir Greyback. At first, he is hostile, but Hermione's determination and her ability to see beyond his monstrous side start to change him. They could end up in a situation where they have to work together to stop a greater evil that is targeting werewolves and other marginalized magical beings. This would involve Hermione using her logical thinking and Fenrir using his knowledge of the werewolf underworld.
One plot idea could be that Fenrir, in his 'good' form, helps Hermione in her research on werewolves. He uses his insider knowledge to guide her in understanding the complex nature of lycanthropy, and they form an unlikely alliance against those who want to use werewolves for dark purposes.
One plot idea could be that Fenrir Greyback, instead of attacking Hermione, is somehow magically bound to protect her. This could lead to a strange alliance where Hermione has to trust a werewolf known for his brutality. Another idea is that Fenrir has a change of heart due to Hermione's intelligence and courage, and he starts to fight against his dark nature for her sake. Maybe he could help Hermione in a battle against the Death Eaters by using his werewolf strength in unexpected ways.
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.
One possible plot could be that Hermione stumbles upon Fenrir Greyback in a situation where he's about to be killed by some dark wizards who see him as a loose end. Hermione, being the empathetic and brave witch she is, decides to save him. Maybe she believes that every life is worth saving, even a werewolf like Fenrir. She could then try to rehabilitate him, using her vast knowledge of magic and her strong moral compass.
One possible plot could be that Fenrir, for some reason, has a change of heart. Maybe he sees Hermione's kindness and intelligence during one of his encounters with the wizarding world. He starts to protect her secretly from other dark forces. And Hermione, initially afraid, gradually realizes there's more to him than just a monster.
Another storyline might involve a time - travel scenario where Hermione goes back in time and encounters a younger Fenrir Greyback. She attempts to change his path, to prevent him from becoming the cruel werewolf he is known to be in the future. This could involve her using her knowledge and magic to offer him a different future, but facing many challenges along the way.
A really interesting plot could be set in an alternate universe where Fenrir Greyback was once a normal wizard but was turned into a werewolf by dark magic. Harry Potter, through some magical accident, finds himself in Greyback's past and tries to prevent his transformation, which would change the course of the entire wizarding world as they know it.
A possible plot could be that Hermione gets bitten by Greyback accidentally. Instead of turning into a full - blown werewolf, she has some new abilities and a strange connection to Greyback. They then have to figure out how to deal with this new situation, while also facing the wizarding world's prejudice against werewolves. It could also involve Hermione using her intelligence to find a cure for herself and in the process, changing Greyback's view of non - werewolves.
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.