One example could be a fanfiction where Harry discovers he has a new and strange power that others in the wizarding world fear. As a result, they ostracize him, thinking he's a threat. For instance, if he could control time in an unpredictable way and the Ministry of Magic, fearing chaos, isolates him.
A fanfiction could explore a scenario where Harry's scar starts to exhibit new and disturbing behavior. Wizards, being superstitious, believe it's a bad omen. So, they ostracize Harry, forcing him to go on a journey to find out the true meaning of his scar on his own.
One popular 'Harry Potter ostracized' fanfiction is 'The Outcast of Gryffindor'. It explores a scenario where Harry is wrongly shunned by his housemates. Another is 'Alone in Hogwarts' which delves into his feelings of isolation. There's also 'Ostracized Savior' that shows how Harry copes when he's pushed to the fringes of the wizarding community.
In some fanfictions, Harry might be ostracized post - war because people are jealous of his fame. He defeated Voldemort and became a hero, but some might resent his status and try to push him aside.
It's popular because it creates a lot of drama. People like to see their favorite characters face challenges, and being ostracized is a huge one. It adds depth to Harry's character as he has to deal with loneliness and betrayal.
One reason could be that it adds a new layer of drama. The original story has Harry as a hero, but in these fanfictions, making him ostracized creates more conflict. It gives writers a chance to explore different aspects of his character, like his resilience.
In some fanfictions, Harry simply ignores the ostracism. He focuses on his own life and continues to do what he believes is right, whether it's helping out at Hogwarts or exploring the wizarding world on his own.
There are also fanfictions where Harry is bullied by his peers in a way that amounts to abuse. They might use magic against him in a harmful way outside of the normal school dueling context, and he has to struggle not only with the physical harm but also the feeling of isolation that comes with such abuse.
Well, in some nightmare fanfictions, Harry Potter might find out that his parents were actually evil all along. This completely changes his view of himself and his place in the wizarding world. Another example could be a fanfic where the magical world is slowly being destroyed by a mysterious force and the characters are powerless to stop it. It creates a very dark and hopeless atmosphere for the story.
One example could be a fanfiction where a character acts completely out of character in a cruel way towards others, like Harry Potter suddenly turning on his friends without any real motivation. Another might be a story that twists the original themes of love and friendship in the series into something cold and unfeeling.
One example could be a fanfiction where Harry Potter visits an Indian wizarding school that has its own unique houses based on Indian values like Dharma, Karma, etc. Another could be a story where Hermione has an Indian heritage and uses Indian magic spells along with the regular ones from the original series.
Fanfiction involving drugs is not in line with the positive values of the original 'Harry Potter' series, and I don't recommend seeking or promoting such content. J.K. Rowling created a magical world full of positive values like friendship, courage and justice, and we should focus on fan works that adhere to these values.