This isn't a chapter fic, but it's a relatively evil!sam and it's pretty long, about 8370 words.
http://dreamlittleyo.livejournal.com/30773.html [NC-17 wincest, just fair warning]

Thanks, sounds interesting.

Here's a multi-story evil!Dean verse. And Sam gets kinda twisted near the end too.
Just start at the bottom:
http://unhobbityhobbit.livejournal.com/tag/evil%21dean+%27verse

You should also read Darker Shade of Black, which is an incredibly twisted AU where both the boys are nuts. Only the one chapter though.
http://sardonicsmiley.livejournal.com/25298.html#cutid1

If you don't mind self recs, Intimations of Morality (http://vorpalblades.livejournal.com/55686.html) is kinda long (over 20,000 words).

I don't mind self recs. Thanks.

Well, it's probably not exactly what you are looking for but kroki-refer (http://kroki-refur.livejournal.com) has written the totally delightful The Awesome Adventures of Andy and Ava (http://kroki-refur.livejournal.com/tag/andy+and+ava) Admittedly both Andy and Ava are dead, but they are fighting crime and evil anyway.

Ooh, Andy and Ava! And it's alright that they're dead, as long as they're still out there being their adorable selves. Thanks.

http://www.sinful-desire.org/archive/viewstory.php?sid=3206&warning=5