Well, there's this abandoned fic(last updated 2009 so yeah) (https://www.fanfiction.net/s/4559734/14/The-Falling)
Basically, any stories out there where Dean deals with the darksides of his soul? Maybe with Michael or Lucifer as a catalyst of sorts, or were actually parts of his souls. Demon Dean is also awesome too.

Not really interested in sex, but hey, if it fullfills the conditions above, then whatever.