There are several places to look. FanFiction.net is one of the oldest and largest fanfic repositories. You can simply type in relevant keywords like 'Naruto', 'Harry Potter', 'final battle' in the search box. AO3 is another excellent option. It not only has a wide range of fanfics but also allows for more detailed filtering. For example, you can filter by the rating of the fanfic, the length, and so on. Some social media groups dedicated to fanfiction might also be a source. People in these groups might share or recommend the 'Naruto the Final Battle Harry Potter' fanfic if they are aware of it.
Yes, there are some. Some fanfics manage to blend the magic of Harry Potter and the ninja world of Naruto in really interesting ways in the context of a final battle. They might have characters from both series using their unique abilities side by side, creating epic fight scenes.
In a Harry Potter final battle fanfiction, Harry might use some new and unexpected spells. For example, he could combine the Patronus Charm with a powerful offensive spell to repel the Death Eaters in a more spectacular way. Maybe he discovers a hidden power within himself that gives him an edge in the fight.
In many fanfictions, after the final battle, Harry might focus on rebuilding Hogwarts. He could use his influence to make it a more inclusive and modern place of magic learning, with new courses perhaps on Muggle technology and its integration with magic.
Obviously, Harry Potter is one of the most important. His role as the Chosen One is central to the final battle. Hermione Granger also plays a crucial part with her intelligence and knowledge of magic. Ron Weasley too, as he provides support to Harry.
The house - elves could be unsung heroes. In fanfiction, they might use their magic in ways that the wizards and witches don't expect. Since they are so good at household magic, they could turn that to their advantage in the battle. For instance, they could make the Hogwarts castle even more of a maze for the Death Eaters to navigate, or they could use their skills to quickly repair any damage done to the castle's defenses.
It could be Luna Lovegood. She has a unique perspective on magic. In the final battle fanfiction, she might use her strange but effective magical items and her unorthodox thinking to outwit Voldemort. For example, she could use some of her Lovegood family's special magical artifacts to create a shield or a trap for the Dark Lord.
Obviously, Harry Potter himself would still be a central character. He would be dealing with the aftermath of the battle, like post - traumatic stress or trying to bring about positive changes in the wizarding world.
One possible plot twist could be that Neville discovers a new and powerful spell that turns the tide of the battle. Another could be that Draco Malfoy has a change of heart and secretly helps the Order of the Phoenix during the final battle.
One interesting plot twist could be that Neville Longbottom discovers a new, powerful spell that can turn Voldemort's own dark magic against him during the final battle. This would change the dynamic of the fight as it gives the good side an unexpected advantage.