Well, Snape confronting the Dursleys could lead to a very interesting scenario. Since Snape has his own complex relationship with Harry, he might initially confront the Dursleys out of some sense of duty towards a fellow wizard, even if he doesn't particularly like Harry. He could put spells on the Dursleys to make them more hospitable or perhaps use Legilimency to find out their true feelings towards Harry. This could then lead to a series of events where the Dursleys are forced to change their ways or face more severe consequences from the wizarding world.
Perhaps in this fanfiction, Snape arrives at the Dursleys' house in a swirl of black robes. He glares at the Dursleys with his dark eyes, filled with a mix of contempt and determination. Snape starts by interrogating them about Harry's living conditions. He might find that the Dursleys have been starving Harry or making him do excessive chores. Snape, being a powerful wizard, could then use his magic to create a more comfortable living environment for Harry within the Dursleys' home. He could also threaten the Dursleys with magic that would make them think twice before mistreating Harry again. This would not only change Harry's situation but also create a whole new dynamic between Snape, Harry, and the Dursleys.
In this fanfiction, Snape might finally expose the Dursleys' ill - treatment of Harry. He could use his magic to intimidate them into treating Harry better. Maybe he'd discover some dark secrets about the Dursleys that they've been hiding all along.
The Dursleys would probably be more frightened. They are muggles and Snape is a powerful wizard. The idea of a strange man in black robes suddenly appearing and using magic would be terrifying for them.
Perhaps Snape would initially mistake the Dursleys for some sort of Muggles with a bit of dark magic in them due to their cruel nature. He could start investigating them, which would cause chaos in the Dursley household as they try to hide their secrets from a wizard like Snape.
If Snape stays at the Dursleys in fanfiction, it could lead to some interesting character interactions. Snape might have a complex relationship with Dudley. He could try to teach Dudley a lesson about bullying, using his Slytherin - like cunning. Or perhaps he'd end up having some sort of begrudging respect for Vernon Dursley's determination to keep the wizarding world out of his family's life, while at the same time finding it completely absurd. And with Petunia, there could be a whole range of emotions, from her fear of him as a wizard to a possible shared understanding of their complex feelings towards Lily Potter.
One possible scenario could be that Hermione confronts Snape about his unfair treatment of Gryffindor students. Maybe she has evidence of him being overly harsh and she stands up to him in a classroom setting.
In some fanfictions, Harry might initially be angry and feel betrayed when he confronts the Order. He could question their decisions and secrecy. For example, he might be frustrated about not being fully informed regarding the plans against Voldemort.
In the 'Daphne meets the Dursleys fanfiction', it's possible that Daphne initially has a hard time understanding the Muggle - like ways of the Dursleys. However, as time passes, she might start to see through their facade. She could then form a plan to get Harry out of that unpleasant environment. For example, she could pretend to be a social worker or something similar in the Muggle world and convince the Dursleys to let Harry go with her. And then she could introduce Harry to the wizarding world in a more positive and gentle way than how the Dursleys have been treating him.
Well, Sirius might be shocked by the Dursleys' treatment of Harry. He could try to rescue Harry from their mean ways.
Well, one possibility is that Draco starts to see the value in the Dursleys' family structure, despite its flaws. He could form an unlikely bond with Dudley, and they might teach each other things. Draco could show Dudley some magic tricks in secret, while Dudley could introduce Draco to Muggle games like football. It could be a really interesting exploration of two different worlds colliding within the Dursleys' household.
One possibility is that Remus meets the Dursleys when he is on some sort of mission related to Harry. He could be there to assess the safety of Harry's living situation. He might find the Dursleys' treatment of Harry unacceptable and try to subtly change things. He could offer to help around the house in a very civilized way, making the Dursleys a bit confused as they are not used to such kindness from the wizarding world. This could lead to a series of events where the Dursleys start to question their own views about wizards and witches.
She might drive the Dursleys crazy with her intelligence and magic knowledge. For example, she could accidentally use magic in front of them while trying to solve some household problems, which would surely shock them as they are so against magic.