Perhaps in a 'harry potter yells fanfiction', Harry yells when he discovers that someone has been spreading false rumors about his friends. He could be in the Great Hall, stand up, and yell at the perpetrator, creating a big scene full of drama and conflict within Hogwarts.
In this fanfiction, Harry might yell during a Quidditch match. Maybe the Slytherin team is using some underhanded tactics to try and win. Harry, seeing his teammates in danger or being unfairly treated, loses his temper and yells at the Slytherin players, which then leads to a series of events that test his leadership skills on the Gryffindor team.
Maybe she's yelling at Ron. Their relationship in fanfictions can be quite complex. If Ron says something insensitive or does something stupid, like forgetting an important task that could put their mission in jeopardy, Hermione would surely yell at him.
Maybe Albus has done something dangerous or disobeyed Harry's instructions. For example, if Albus got involved with some dark magic related stuff without Harry's knowledge, that would surely make Harry yell at him.
Maybe a spell goes wrong and causes a character to develop diabetes. The story could then be about how they adapt to this new situation. They might search for a magical cure within the wizarding world, or learn to live with it with the help of their friends, like Hermione using her research skills to find suitable magical remedies or ways to manage it.
Maybe Harry discovers a hidden part of Hogwarts where a Wendigo has been lurking. He has to use his magic skills to either defeat it or find a way to coexist with it.
In a fanfic, it could be a scenario where Tonks has been secretly admiring Harry for his bravery. One day, Harry accomplishes something really great and Tonks, overjoyed, yells'mine' in a sense of pride, like he's part of her group of heroic people she admires, and hugs him tightly. For example, when Harry manages to defeat a powerful dark wizard on his own.
Maybe James Sirius Potter did something really reckless. For example, he might have put himself in danger while exploring some forbidden areas in Hogwarts. Harry, having gone through a lot of dangerous situations himself, would be worried and yell out of fear and frustration.
One plot idea could be that Tony Stark somehow travels to the wizarding world. He could use his technological knowledge to improve the wizarding devices. For example, he might make brooms fly faster with some kind of engine modification.
Well, one plot idea could be that Harry discovers he has a special gift for breeding magical animals that no one else has. He starts breeding rare and endangered magical creatures secretly in the Forbidden Forest. Eventually, his activities are discovered, but instead of getting in trouble, he is asked to help save the magical animal population in the wizarding world.
One plot idea could be that Harry discovers his new 'God of Mischief' status and uses it to outwit Voldemort in unexpected ways. For example, he could create illusions that drive Voldemort's followers crazy or play tricks on Death Eaters during battles.
One plot idea could be that Henrik Mikaelson somehow gets transported into the 'Harry Potter' universe. Maybe he has his vampire powers and has to hide them among the wizards. He could form an unlikely friendship with Harry and help him in his battles using his unique abilities.