There are fanfictions where Harry uses his connection with magical creatures. He befriends a group of powerful and intelligent magical creatures, like the centaurs. They come to Hogwarts and, through their own means, intimidate Umbridge so much that she leaves. The centaurs could use their wisdom and their own form of magic to make Umbridge feel unwelcome and out of place, until she finally decides she has no choice but to go.
In some fanfictions, Harry discovers a long - forgotten magic charm that has the power to make a person's worst nightmares come true. He uses it on Umbridge, and she is so terrified by the nightmares that she runs away from Hogwarts. The charm could be something that is based on the person's deep - seated fears, and for Umbridge, it might be related to losing her power and being publicly shamed.
One creative way is by using his Patronus in a unique way. His Patronus could be made to deliver secret messages to the other students right under Umbridge's nose. Since she can't really stop a Patronus, Harry uses it as a communication tool to organize against her rules.
Snape could face some backlash from the Ministry. If they find out that he was involved in getting rid of Umbridge, they might try to find ways to punish him or at least keep a closer eye on him. However, his skills at subterfuge would likely help him avoid any serious consequences.
In some versions, Snape uses his knowledge of the Dark Arts and Hogwarts' secrets. He might set up a situation where Umbridge is lured into a restricted area of the castle and gets into trouble with some magical creature or ancient magic, causing her to be removed from her position.
In some fanfictions, Harry might use his powerful magic skills, like advanced spells he's learned secretly, to outwit Umbridge. For example, he could create a series of complex illusions that confuse her and lead her to leave Hogwarts on her own.
Fred and George Weasley are also favorites. Their mischievous nature can be amplified in fanfictions. They could create new and even more spectacular magical pranks specifically aimed at Umbridge, like turning her office into a never - ending maze of trick stairs and hidden rooms filled with various magical creatures that drive her crazy.
One creative prank could be that Harry uses magic to make Umbridge's quills write only nonsense whenever she tries to write a decree. Another could be that he enchants her office so that every time she sits in her chair, it makes a loud and embarrassing noise, like a donkey braying. And he could also charm her teacup to refill with a really bitter-tasting potion instead of tea.
Hermione is a must. Her intelligence and extensive knowledge of magic and Hogwarts rules would be invaluable. Ron would be involved too. He's Harry's close friend and has a bit of a mischievous streak himself. Fred and George Weasley are very likely to be part of it. They are known for their love of pranks and their dislike of authority figures like Umbridge. Luna Lovegood could also be included. She has a unique perspective and might come up with some really out - of - the - box ideas for Harry's revenge on Umbridge. Plus, her presence would add an interesting and somewhat dreamy element to the whole revenge plot.
In some fanfictions, Harry might use his magic skills in a creative way to embarrass Umbridge. For example, he could make her signature pink outfits turn into ridiculous colors every time she tries to be authoritative. Another scenario could be that Harry reveals some of Umbridge's darkest secrets in front of the whole school, which would surely be a form of revenge as she values her reputation so much.
Often, Harry uses his intelligence and courage. He could find loopholes in Umbridge's rules and use them against her. For example, if she made a rule that was against the school's original code, Harry could prove it and get her in trouble. Another way is that he could get the support of the magical creatures at Hogwarts. If the centaurs or the house - elves had a problem with Umbridge, Harry could use that to his advantage to get her fired.
A common plot in 'Harry Potter Dolores Umbridge Fanfiction' is her getting a taste of her own medicine. For example, in some stories, she is put through the same strict and cruel rules she imposes on others. It's a satisfying plot for those who dislike her character in the original books.