4x02 "Are you there God? It's me, Dean Winchester" Rewatch
See end of post for Destiel analysis.
Bonus Destiel analysis:
Let's look at this ep from a power perspective. Power is great for explaining the way BDSM works but it's also a major facet of a person's personality development too.
This episode was pretty much about the impossible standard Dean tries to hold himself to, to save everyone he can while mitigating as much damage as possible, and all of the ghosts were pretty much just twisting the shit out of that knife.
He kind of puts himself above everyone in that way, people to be saved or women to be conquered. He has a bit of a power trip going on constantly in an effort to subdue is total lack of ego.
But when he sees Cas? It's all why didn't you do more? What we find is that Castiel is the only thing that Dean holds in as high of a regard as himself. Castiel is the only thing Dean can see eye to eye with. Cas is the representation of the standards to which he holds himself.
Cas is a foil to Dean, who just spent 40 years in hell. Dean is jealous of Cas, jealous of Cas's power and his apparent misuse of it not to save the huddling masses. He looks up to Cas in that he's everything Dean wants to be, but down on Cas for being so similar to himself, whom he hates.
If this is the beginning of their relationship, what this means in graphical terms is that as soon as Dean can learn to love and accept himself, he'll learn to love and accept Castiel too, and vice versa. This inception point of their relationship is their darkest hour. They're both lost and alone and blind, but they're already sowing the seeds for growth. Dean can make Cas see that the minutia matters just as much as macro problems. Cas can make Dean see that he's not above anyone and that he deserves self-worth as much as the next person. They are perfect and complex counterparts to one another.