Found! Specific Fic: Dark Sam and Self-Destructive Dean Getting in Fights - Down the Road by Morgan
Hello, all! Thank you very much for reading!
I am looking for a Supernatural fic and I am unsure whether it is explicitly Sam/Dean or rather gen with lots of UST and codependence, but I do happily have some other details. The fic is a dark one that focuses closely on Sam and Dean on the road without much of a supporting cast of canon characters. It features a self-destructive Dean and several barfights. I believe it is set fairly early in the show's timeline (definitely pre-season eight, possibly even as early as S2 or S3).
Early in the story, Sam watches Dean goad two men into a streetfight who have followed them from a bar. At first it seems like Sam disapproves of Dean's behaviour, but Sam encourages the fight by betting on Dean and basically watches Dean demolish them.
Later in the story, Dean gets in a different barfight in front of a crowd and has to surreptitiously get Sam to retrieve Dean's gun so the situation won't escalate completely out of control. People in the crowd jeer, referring to Sam as something like Dean's boyfriend, owner, or pimp.
I believe the story is largely from Sam's POV: their relationship may or may not be sexual, but it's definitely claustrophobic and unhealthy. Sam enables Dean's self-destructive behaviour and closely watches it. I'm unsure whether Dean is more straightforwardly dark or merely out of control. The psychology of the boys' relationship is complex and often suggested rather than being clearly laid out and it might have one of those gut-punch endings.
If someone is able to help, I will be thrilled to update the confirmed tags for future searchers. Thanks again!
(Just as a note, this is not traveller's excellent 'any which way you can')