I just read an incredible dark!Dean fic that starts preseries and ends in season 7, if that's something you'd be interested in. It's Sam/Dean, and it's seriously dark, so take the author's warnings seriously. Scratch (http://archiveofourown.org/works/861633/chapters/1651321) by steeplechasers: "Dean's been fixated on Sam all his life; it's no secret. It's only when Sam abandons him for normalcy that his obsession becomes something darker, more necessary--and incredibly violent. And even when Sam comes home to him, there's no guarantee that Dean will ever be the same."