In this fanfic, Grindelwald could be teaching Harry about his own grand plans for the wizarding world. He might try to convince Harry that his ideas of a new wizarding order, where wizards are not in hiding but ruling over Muggles, are actually for the greater good. Harry, being the hero he is, would be conflicted between what he has always believed in and what Grindelwald is presenting to him.
Perhaps Grindelwald teaches Harry about the history of magic in a very different way than what Harry has learned before. He might show Harry the secrets of magic that have been hidden by the wizarding world's authorities. This could lead Harry to question the existing order and his own beliefs. Maybe Harry starts to see the gray areas in the battle between good and evil.
One possible plotline could be Harry initially being forced into the training but then gradually getting intrigued by Grindelwald's knowledge. He might start to question the traditional teachings of Hogwarts. Another could be that Harry is tricked into the training, thinking Grindelwald has good intentions only to discover the truth later.
Maybe Sakura teaches Sasuke about emotional control. Sasuke has always been brooding and angry, and Sakura, with her more empathetic nature, could show him how to manage his emotions better. This could lead to Sasuke becoming a more well - rounded ninja and a better teammate.
One plotline could be Harry's discovery of his relation to Grindelwald. Maybe he finds an old family heirloom or a hidden letter that reveals the truth. Another could be how the wizarding community reacts to this news. Some might fear Harry, thinking he has inherited Grindelwald's dark tendencies.
A plotline might involve the magical community's reaction. Since Grindelwald was a feared dark wizard, when the news spreads that Harry is his grandson, there could be a lot of chaos. Some might fear that Harry has inherited Grindelwald's dark tendencies. However, Harry could use this situation to prove that one's upbringing and choices matter more than blood relation. He could embark on a journey to clear the name of the Potter family and show that he is different from his grandfather.
One possible plotline could be that Harry, with his knowledge of the Dark Arts from his own experiences, tries to show Tom the true nature of defensive magic. He might start by teaching basic spells like the Shield Charm. Harry could also share his insights on how to resist the allure of the Dark Arts, which is something Tom struggles with in his later years as Voldemort.
One possible plotline could be that Harry realizes the wizarding world has some deep - seated flaws that Voldemort also wants to change. So, they form an alliance to reform the Ministry of Magic. For example, they might work together to end the pure - blood supremacy that has long plagued the wizarding society.
One possible plotline could be that Professor Riddle, perhaps a relative of the infamous Voldemort (Tom Riddle), initially has a strained relationship with Harry. He might be suspicious of Harry due to his family connection to the Potters. However, as the story progresses, they could discover they have more in common than they thought, like a shared interest in some arcane magic. And they might end up working together to solve a mystery within Hogwarts that threatens the entire wizarding world.
One possible plotline could be Bellatrix trying to mold Harry into a dark wizard. She might use her knowledge of the Dark Arts to teach him, but Harry resists. Another could be that Bellatrix starts to have a change of heart while raising Harry and begins to question her loyalty to Voldemort. Maybe she sees something in Harry that reminds her of a better part of herself.
Maybe Harry leaves the wizarding world and uses his magical skills in the muggle world as a mercenary. He could be hired for dangerous jobs that require a touch of magic but need to be kept secret from the muggles.
In a 'Grindelwald Adopts Harry' fanfic, Grindelwald could be seeking to create an heir of sorts. He adopts Harry when he is very young. Grindelwald might expose Harry to a world of magic that is different from what he would have known at Hogwarts. Harry could be taught magic that is more about power and control. However, as Harry gets older, he might discover the truth about Grindelwald's dark deeds and his plans for the wizarding world. This could lead to a great internal struggle within Harry as he has to choose between the man who raised him and what he believes is right for the wizarding community as a whole. There could be a lot of drama as Harry tries to find his place and figure out his true identity in this new and rather dark scenario.