The most interesting part is the crossover of different powers. For example, seeing Thor's lightning powers interact with Harry's magic spells is really cool.
One popular pairing is Harry Potter and Captain America. They both have a strong sense of justice and leadership. People like to imagine them sharing their experiences and learning from each other. Another is Hermione and Tony Stark. Hermione's intelligence and thirst for knowledge would match well with Stark's genius in technology.
One interesting crossover could be the use of magic in the Avengers' world. For example, Harry Potter characters could teach the Avengers spells to enhance their fighting abilities. Another aspect could be the character interactions. Imagine Hermione trying to figure out the science behind the Avengers' technology. Or Thor and Hagrid becoming friends over their love for large and powerful creatures.
First, you need to understand the characters well. Know their personalities, powers, and goals. For example, Thor is a powerful Asgardian with his hammer (or axe in Endgame), and Harry Potter is a young wizard with a strong sense of justice. Then, think of a plot that can bring these two universes together. It could be a crossover of villains, like Loki and Voldemort teaming up.
One great 'Harry Potter Avengers Endgame fanfiction' is 'The Wizarding World Meets the Avengers'. It combines the magical elements of Harry Potter with the superhero action of Avengers Endgame in a really exciting way.
It could be a wild adventure where the wizards from Harry Potter use their magic to help the Avengers in the final battle of Endgame. Maybe Harry could use the Disillusionment Charm to sneak up on Thanos, or Hermione could use time - turning magic similar to what happened in the Prisoner of Azkaban to change the outcome of some of the events in Endgame.
Well, first of all, the Avengers would need to locate Harry Potter. Maybe Hawkeye could use his eagle - eyed skills to spot him. Then, Captain America could lead the team in a rescue mission. Hulk could be the muscle, smashing through any obstacles in their way. Black Widow could use her combat skills to take out any enemies nearby. And finally, they could use the Quinjet to escape with Harry to safety.
In fanfiction, Raven could be an interesting addition to the Harry Potter and Avengers universes. Maybe she has some sort of magic ability that links her to the wizarding world of Harry Potter and at the same time, she might possess powers that could make her fit into the Avengers' world. For example, she could be a powerful witch who also has enhanced physical abilities like the superheroes in the Avengers. She might interact with Harry Potter characters by using her unique powers to solve some magical problems at Hogwarts. And in the Avengers' side, she could be a new recruit with her own set of skills and backstory.
A petal could potentially be a character's name or nickname in a fanfic that combines Harry Potter and Avengers. It could be a magical petal that has the ability to transport characters between the two universes. For instance, if a character from the Avengers picks up this petal, they might suddenly find themselves in Hogwarts. Or perhaps it's a petal from a dark magical plant that is being used for evil purposes by a villain who has knowledge of both magical worlds.