Well, one possibility is that Harry gets revenge by using the Marauder's Map to outwit Umbridge. He could lead her on a wild goose chase around the castle, making her look foolish as she stumbles into all kinds of dead - ends and secret passages. Also, he might use his connections with the magical creatures to play tricks on her. Like getting the centaurs to give her a good scare when she ventures into the Forbidden Forest.
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.
There could be a fanfiction where Harry uses his knowledge of potions to get revenge. He might create a special potion that makes Umbridge's voice so high - pitched that it becomes unbearable for everyone around her. Or perhaps he finds a way to make all of her quills write only embarrassing things when she tries to use them for discipline. Harry could also enlist the help of his friends, like Hermione, to come up with a really elaborate plan to take Umbridge down a peg or two.
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 another scenario, Harry could expose all of Umbridge's wrongdoings in a very public and embarrassing way. He might use the Marauder's Map to find evidence of her sneaky activities and then present it to the whole school, causing everyone to turn against her and forcing her to leave in disgrace. Harry has a lot of friends who would support him in this, like Hermione and Ron.
One interesting scenario could be that the removal process involves a unique magical spell that only Harry, with his special connection to Voldemort, can perform. This spell might require him to draw on his deepest reserves of courage and love for his friends.
One interesting fanfiction could be about Umbridge getting a taste of her own medicine. Maybe the students use magic in a clever way to make her face the consequences of her cruel actions without getting caught themselves. Another could be a story where Umbridge has a change of heart due to some magical event that shows her the error of her ways, but still has to face the wrath of the students she's wronged. And there might be a fanfic where Umbridge is transported to a different magical world and has to learn to adapt and deal with new rules and cultures.
Another plot could be that Umbridge is forced to work with Harry and his friends against a greater evil. This would be a huge shift as she hates them so much in the original. But in the fanfiction, they might have to put aside their differences when a new dark wizard emerges, more powerful than Voldemort, and they realize they need all the help they can get.
One possible scenario could be that Harry discovers some long - hidden secrets about Dumbledore that he feels were used to manipulate him. So, he might expose these secrets to the wizarding world, ruining Dumbledore's once - sterling reputation. Another could be that Harry uses his own skills and the support of his friends to undermine Dumbledore - related policies or institutions in Hogwarts that he believes were unfair.
Well, it could also be Harry who is wrongly thought to be cheating on his partner. In the fanfiction, perhaps some false rumors are spread by his enemies. They create a situation where his friends start to doubt him, and his relationship is put under great strain.
There could be a fanfiction where Hermione comes up with a brilliant prank. She uses a spell to make Umbridge's parchment write out all the unjust rules she has made instead of whatever Umbridge is trying to write. Every time Umbridge tries to write a memo or a note, the parchment just keeps repeating things like 'No groups larger than three' and 'No fun allowed' over and over again, driving her mad.
I'm not sure there are many 'lemony' fanfictions that are appropriate to recommend, as they often involve inappropriate or adult - themed content. However, there are some great non - inappropriate fanfictions about Umbridge that focus on her tyranny at Hogwarts. For example, some fanfictions explore how the students band together to resist her rules in creative and magical ways.
One interesting plotline could be Harry leading a secret resistance against Umbridge within Hogwarts. He might use his skills in the DA (Dumbledore's Army) to outwit her at every turn. For example, they could use magic in clever ways to undermine her rules without getting caught.