In some fanfictions, the bane could be a special bond that forms between Harry and his friends. This bond gives them the strength to resist Voldemort's influence on a whole new level. They are able to combine their magic in a way that was previously thought impossible. It could be that their friendship and loyalty are what truly make them Voldemort's bane.
One interesting plot could be the discovery of a new magic that is the true bane of Voldemort. This magic might be something that has been long forgotten in the wizarding world and Harry stumbles upon it during his quest to finally defeat Voldemort.
Perhaps a plot where the bane is not a weapon or a spell but a person. A character who has been hidden away all this time, with a power that can nullify Voldemort's dark magic. This person could be a descendant of an ancient wizarding family that has been in hiding for centuries. Their connection to the original magic that founded Hogwarts could be the key to Voldemort's downfall.
One idea could be a fanfiction where Voldemort has a change of heart due to some ancient magic. Maybe he discovers a spell that shows him the true consequences of his actions and decides to work with Harry to fix the wizarding world instead of destroying it.
One idea could be that Harry, influenced by dark magic, forms an uneasy alliance with Voldemort. They could team up to take over the wizarding world in a different way than Voldemort originally planned, perhaps by ruling jointly. Another plot could involve Harry exploring the darker aspects of his own magic and using some of Voldemort's knowledge to do so, which causes a rift between him and his friends.
One idea could be a fanfiction where Voldemort gets a second chance at life but without his dark magic powers. He has to learn to live as a normal wizard in the wizarding world and Harry Potter has to decide whether to trust him or not.
One possible plot could be that Harry discovers the truth about his heritage as he gets older. This causes a huge upheaval in the wizarding world. His friends might be initially shocked and some might even turn against him. Harry then has to struggle to prove that he's not like Voldemort while also trying to understand his new - found identity.
Well, one possible plot could be that Voldemort's daughter tries to redeem the name of her father. She might struggle with the dark legacy she has inherited while also being drawn to the world of Hogwarts and the light. Maybe she forms an unlikely friendship with Harry Potter, which causes a stir among both the Death Eaters and the Order of the Phoenix.
One idea could be that Harry discovers a new spell that can penetrate Voldemort's dark magic defenses and uses it to shoot him. Another could be that Harry teams up with some unexpected allies, like the house - elves, who help him get in a position to shoot Voldemort. Maybe Harry has to sacrifice something important, like his invisibility cloak, to gain the power needed to fire the shot that will defeat Voldemort.
One interesting plot idea could be that Harry discovers a new and ancient magic that gives him an unexpected edge in the duel. For example, he might find a spell that can temporarily freeze Voldemort's dark magic, allowing Harry to strike. Another could be that Harry has a vision during the duel that shows him the true source of Voldemort's power, and he uses this knowledge to target it directly. Maybe it's a hidden object or a bond with a dark entity that Harry manages to sever, weakening Voldemort.
One idea could be a story where Bellatrix has a moment of doubt about Voldemort's methods. Maybe she starts to see the destruction he's causing and has to decide whether to stay loyal or turn against him. And Harry Potter could somehow be involved in this internal struggle of hers, perhaps by showing her a different path through his own actions and values.
Maybe Harry absorbs Voldemort and then has to deal with the internal struggle of Voldemort's thoughts within his mind. He constantly battles Voldemort's voice, which tries to persuade him to use power in a wrong way. But Harry uses his own strong will and the love he has for his friends and family to overcome it.
One idea could be that through the mind link, Harry discovers Voldemort's hidden fears from his past, like his fear of being abandoned as an orphan. This could give Harry an edge in their final battles.