Definitely Hermione. She could research Umbridge's past and find some dirt on her that they could use against her. Neville might also be a great help. He has grown a lot in courage throughout the series. He could stand up with Harry and help rally the other students. The house elves might also get involved. They are often overlooked but they know a lot about what goes on in Hogwarts. They could provide some crucial information about Umbridge that Harry could use to get her out. And don't forget Ginny. She's feisty and not afraid to take action. She could use her charm and quick thinking to support Harry in his quest to remove Umbridge.
His friends like Ron and Hermione would surely be there to assist him. Ron could use his strategic thinking and Hermione her vast knowledge of magic. They might come up with a plan to expose Umbridge's wrongdoings which would lead to her being kicked out. Also, the Weasley twins could play a big role. They are known for their pranks and could use their creativity to make Umbridge's life at Hogwarts so miserable that she'd have no choice but to leave. And Dumbledore, even if he has to be a bit more subtle in his actions, could give Harry some guidance behind the scenes.
Well, in this fanfiction, Harry could be helped by Luna. Luna has a unique perspective on things and might be able to see through Umbridge's false facade in a way others can't. She could point out things about Umbridge that seem off to Harry. Hagrid could also be of assistance. He has a lot of influence among the students and the magical creatures of Hogwarts. He could use his popularity to gather support for Harry's cause. Additionally, some of the older students who have been at Hogwarts longer and seen more of Umbridge's tyranny could join forces with Harry. They could use their experience and knowledge of the school's politics to help get Umbridge out.
Well, perhaps in the fanfiction Harry finds out that Umbridge has been secretly working for Voldemort all along. He gathers evidence and presents it to Dumbledore and the other teachers. They are shocked and immediately decide that Umbridge can no longer stay at Hogwarts. Harry takes the lead in escorting her out of the school. Or maybe Harry uses his connection with the Order of the Phoenix to get support in getting rid of Umbridge. The Order members come to Hogwarts and together with Harry, they force Umbridge to leave because of her unjust and cruel treatment of the students.
His friends for sure. Hermione is really smart and could help with things like making sure the baby is healthy with magic, and also helping with any magical problems that might come up because of the baby.
One possible reason could be that in the fanfiction, the wizarding community in England has turned against Harry due to some false accusations. Maybe a powerful dark wizard has framed him for a series of heinous crimes, and the public, being misled, forces him to leave. Another reason might be political intrigue within the Ministry of Magic. There could be a new regime that sees Harry as a threat to their power and thus kicks him out.
Harry might be initially shocked and angry. He has always considered England his home and fought for it. So, being kicked out would be a huge blow. He may try to fight back, using his magic to resist the unjust decision. However, if he realizes that resistance is futile, he could leave with a sense of bitterness and a determination to one day clear his name.
The magical creatures could play a role in helping Harry. For example, the centaurs with their deep understanding of the stars and magic could offer their wisdom. The house - elves, like Dobby (if he's alive in the fanfic), might use their unique magic to assist Harry in a time of need.
Well, perhaps in the fanfiction, Harry has a vision of a different future for himself that doesn't involve traditional Hogwarts education. He might have seen a path where he can make a greater impact on the wizarding world without the constraints of school. It could also be that he's being influenced by a new character in the fanfiction, someone who convinces him that there are better ways to develop his magic and knowledge outside of Hogwarts. This new influence could be from a different magical culture or a rogue wizard with unique ideas.
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.
Maybe Harry has a big fight with Ron over something like Ron's lack of trust. For example, if Ron doubts Harry's intentions again as he did in the original story. Harry, in a fit of anger, kicks Ron out of Grimmauld Place.
In some versions of this fanfiction, it could be Neville. He also had a difficult family situation, so he might be more attuned to signs of distress in Harry. Maybe he notices Harry's worn - out clothes that are too big for him, which could be a sign of neglect, and then starts to piece together that something is wrong at the Dursleys'.
One reason could be that he was under a dark spell cast by a new enemy in the fanfiction. Maybe some dark wizard or witch sent a spell his way before he boarded the train, and it took effect during the journey.