In a 'Harry Potter gets angry' fanfiction, he could be enraged when he realizes that some old pure - blood families are still trying to undermine the new order at Hogwarts. His anger might fuel him to confront these families directly, leading to intense magical duels and a struggle for the future of the wizarding school.
One example could be a fanfiction where Harry is angry at the Ministry of Magic for their continued interference in Hogwarts affairs. He might take matters into his own hands and start a rebellion of sorts among the students to fight for the school's independence. Another could be Harry being angry with Draco for some new scheme and they engage in a more intense rivalry than in the original books.
In the 'Harry Gets Angry' fanfiction, Harry might get angry when his reputation is smeared. He has always been in the spotlight, and false rumors can really get to him. Also, seeing the weak or the underdogs being bullied can make him angry. He has a strong sense of justice, so any form of oppression or unfair treatment towards others can stir his anger as well.
In some 'Goku Gets Angry' fanfiction, a common scenario is when his friends are in danger. For example, if Vegeta is seriously injured by a powerful new enemy, Goku's anger flares up. He then enters a new and more powerful form to fight the foe. Another scenario could be when the Earth is threatened. Maybe a villain plans to destroy the planet, and Goku gets angry at the thought of his home and family being in jeopardy. This anger gives him the motivation to train harder and find a way to defeat the villain.
One common theme is betrayal. Harry often feels betrayed by those he trusts, like the Ministry of Magic or certain teachers, and his anger stems from that. For example, in some fanfics, he discovers that they have been using him for their own purposes.
In some fanfictions, Harry Potter might be angry at the Order because he feels they are keeping secrets from him. He is used to being in the thick of things and when the Order withholds information, it can make him feel left out and untrusted.
He might lash out with his magic. For example, he could send a spell flying at the source of his anger without really thinking. Sometimes, he just glares intensely, his green eyes filled with fury. And he may raise his voice, shouting at those who have angered him.
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.