Let's talk about endings first. The best fics that carve out their own finale almost always have to break from the show's later-season trajectory, because honestly, after a certain point the canon plot became such a tangled mess it's a miracle anyone could follow it. I look for stories that treat the sire bond as the narrative dead-end it was and just... ignore it, building toward something more cohesive.
One standout is 'The Unraveling of Time' over on Ao3. It's a Bonora-centric piece that posits Bonnie's psychic abilities allowing her to perceive fractured timelines. The ending isn't about a grand battle or a wedding; it's this quiet, profound moment where she chooses to seal off the supernatural from Mystic Falls permanently, but at the cost of her own memories. Everyone gets to live a normal, human life, including Damon and Stefan, but none of them remember why it feels so bittersweet. It's melancholic and original, completely sidestepping the usual 'who does Elena choose' finale.
Another is 'Carved in Marble, Written in Blood,' which is a Katherine-centric redemption arc that ends with her sacrificing her immortality not for a man, but to become the anchor for the Other Side, a permanent guardian spirit. It gives her agency and a purpose the show never did. The author built the whole story around the idea that her ending should be about legacy, not love, and it works.
You have to dig through a lot of 'happily ever after with Damon' stuff to find these, but the search is worth it. They feel like legitimate alternate-series finales, not just extended episodes.