I WANT the brothers to have a very intense relationship and be willing to die for each other.
I DON’T want them to have a toxic dependence on each other that’s so over the top they would each sacrifice the world, or even one single innocent person, rather than let go of each other.
To me it’s very clear where the line is drawn between those two things. Sam looking for Dean, after he mysteriously disappeared in a supernatural event, would have been firmly on the good side. The way their relationship had been portrayed up until then, I couldn’t accept that Sam would just put Dean (and Kevin, and Cas for that matter) behind him and blithely get himself an apple pie life.
What happened later in season 8, however, when Sam and Dean ditched Amelia and Benny, respectively, because any closeness to other people was a threat to their relationship – that was unhealthy. That was dark. That was the bad side. It was the first inkling I got that they were about to start sacrificing more and more other people on the altar of the bro-bond.
And they did. In the season 8 finale, they allowed Hell to stay open so Dean wouldn’t lose Sam. In season 9, they got Kevin killed. In season 10, they got Charlie killed, released the Darkness and killed Death. All so they could keep holding on to each other. The stakes can’t get much higher than this. Something has got to give.