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.
Well, perhaps Bellatrix discovers a prophecy that involves Harry being crucial for the future of the wizarding world in a way that benefits her own interests in the long run. So, she steps in to save him. It could also be that she has a secret love for Sirius Black (Harry's godfather), and since Harry is related to Sirius, she decides to save Harry out of some twisted sense of loyalty to Sirius.
Another plot could be that as Harry raises Tom, he discovers some hidden good in Tom that was overshadowed by his later actions as Voldemort. Harry might then use this discovery to try and rewrite the future, preventing all the destruction that Voldemort caused. He could encourage Tom's magical abilities in a positive way, like getting him involved in helping others with magic instead of using it for domination.
One possible plotline could be Bellatrix's unwavering loyalty to Voldemort being tested. Maybe she discovers something about Voldemort's past that makes her question her blind devotion. For example, she could find out about some of his more cowardly actions that he has kept hidden from his Death Eaters. Another could be a scenario where Bellatrix tries to prove herself even more to Voldemort by taking on a dangerous mission that he initially doubts she can handle. This could lead to a deeper understanding between them, or it could backfire and cause a rift.
One possible plotline could be Tsunade teaching Naruto more about medical ninjutsu. Since she is a great medical ninja, she could pass on her knowledge to Naruto, which would add a new dimension to his skills. Another aspect could be her guiding Naruto in leadership, as she is the Hokage. This might help Naruto in his future role as a leader in the village.
Perhaps Walburga realizes that Harry is the key to changing the wizarding world for the better. She could start teaching him about the history of the Black family, both the good and the bad, and together they could work towards a more inclusive and less prejudiced wizarding society. This would be a major shift for her as she comes from a family with a lot of dark and prejudiced views.
In some fanfictions, Bellatrix might save Harry because she is magically bound to him in some way. Maybe a spell backfired and now she has to protect him. Or perhaps she has a secret love for Sirius Black (Harry's godfather) and in order to honor his memory, she saves Harry. There could also be a plotline where Bellatrix is tired of Voldemort's tyranny and sees Harry as the one who can overthrow him, so she saves him for the greater good of the wizarding community.
One possible plotline could be that Bellatrix is somehow brainwashed or redeemed early on. Harry, seeing the potential for good in her, tries to help her further. Over time, they develop feelings for each other and end up getting married. Another could be a time - travel scenario where Harry goes back in time and changes Bellatrix's path before she becomes a full - fledged Death Eater, leading to their relationship and marriage.
It's possible. One way could be to have a time - travel or alternate universe scenario. Maybe Harry goes back in time and meets a younger Bellatrix before she fully turns to the dark side. He could see the potential for good in her that was later corrupted by Voldemort. For example, he might find out that she had some doubts about the Dark Arts initially but was pressured into it.
Well, a plot might involve Bellatrix being involved in some sort of forbidden magic experiment at Hogwarts. She could be trying to impress the Dark Lord even as a student. Or it could be about her trying to undermine Dumbledore's authority at Hogwarts. For example, she might spread rumors or cause small acts of chaos around the school to show her disdain for the more light - hearted and inclusive Hogwarts environment.
A possible plotline could start with Bellatrix having a strange fascination with Harry from the start. She manages to get him in her clutches and treats him like a pet. Harry, on the other hand, uses his wits and the limited magic he can access in this state to outsmart Bellatrix. There could be a lot of psychological battles between them, with Harry trying to understand Bellatrix's twisted mind while she tries to break his spirit. And all this could be set against the backdrop of the ongoing war between the good and the evil in the wizarding world.