Title: Take the Long Way Home
Word Count: 24,509
Warnings: Major character death (doesn't stay that way, no explicit descriptions); mentions of rape and torture in the past; strong language
Summary: Sam finds a way to "fix" demon!Dean, but there's a catch. He has to kill him to do it. And as horrible as it is, Sam does it because it's the only way to get his brother back. The good thing is, Dean comes back "normal." The bad thing is, he turns demon again after six months, and Sam has to kill him again to get him back. Long story short, this is one vicious cycle, not just because of the killing and dying thing, but because every time Dean comes back "normal," he's really pretty damaged and doesn't remember a thing about what happened before. Can Sam find a way to stop the cycle before it's too late? Before Dean becomes so damaged there's nothing left to bring back?
PART ONE - PART TWO - PART THREE - PART FOUR -
PART FIVE - PART SIX - PART SEVEN
READ IT ON AO3