Well, in some fanfictions, the legendary sword might be enchanted with special powers like being able to cut through any dark magic. It could also have a mind of its own and only allow Harry to wield it when he's in a pure - hearted state.
Well, it could potentially give him an edge in combat. Maybe he can use it to defeat dark creatures more easily. For example, if he faces a Dementor, the sword might be able to disrupt its form in a way normal spells can't.
Yes, there are many. In some fanfictions, the sword might have the power to cut through any dark magic. For example, it could be able to destroy Horcruxes more easily than in the original story. It might also have the ability to protect the wielder from the most powerful curses.
Harry Potter himself is often associated with it. After all, he's the main character in the original series and it makes sense for him to be connected to the legendary sword in fanfictions. He could use it to fight Voldemort in new and exciting ways.
The sword might be a gift from a mysterious magical being. This being saw potential in Harry Potter and decided to give him the sword as a tool to help him in his future battles. It could have been enchanted specifically for Harry to face the unique challenges he will encounter.
There might be. Fanfiction writers sometimes like to take characters out of their comfort zones and explore darker or more extreme scenarios. But in the official 'Harry Potter' lore, Harry would never casually use the Killing Curse. It's a very serious and immoral spell in the wizarding world.
One fanfic that might fit this is 'The Female Harry's Adventure with the Sword'. In it, the female Harry Potter discovers an ancient sword and uses it to face new and unique challenges in the wizarding world. It's a really interesting take on the character and the addition of the sword brings a fresh element to the story.
In some fanfics, the sword is enchanted and has a mind of its own. The female Harry Potter has to form a bond with the sword, almost like it's a living being. This leads to some really interesting character development as she learns to communicate with the sword and use its powers to her advantage. She might have to face her own insecurities and fears as she does this. Also, the sword could be a symbol of a new era in the wizarding world, and her using it could spark a revolution or change in how magic is perceived and used.