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I hate to defend late season writing & I definitely see feeling like Dean not just pointing the gun at Sam but also (more so) being willing to sacrifice everyone else for his own freedom is out of character; in the grand scheme of Dean Winchester, of course those things are. #spn 
But here's why it works in this specific context & why that scene made a lot snap into place for me. First of all, he's up against something that apparently was enough to put an end to every other universe: God wrote this ending. That alone should excuse any behavior, in theory.
That's bad narrative. That's why God being in story was such a colossal mistake. Now that there's a God, he can make them do anything. What they do has no value & doesn't have to make sense. I still think these things are true & bad storytelling, but it's the journey Dabb chose.
So accepting that as we must, Dean's desperation & acting out makes perfect sense & is in fact more relatable to me than most things that happen in their larger-than-life existence. He is, as a character, lashing out against the same thing I have been railing against as a viewer.
I don't think Dean, when he pulled that gun on Sam, believed for a second he would shoot. I don't think we as viewers were supposed to be worried. Chuck believed he would because he built the entire world to push Dean into that. Chuck pointed the gun at Sam. Dean didn't shoot it.
That's where the characterization lies for me & where "aha!" moment clicks. Here is Dean Winchester, who we have known for 15 years of our lives &, idk, roughly 95 years of his. &, as Sam points out, that whole time his thing has always been to protect person he's pulling gun on.
Protecting Sam as his personal priority is a microcosm for the Winchester's greater purpose. Sam & Dean's cosmic purpose...in Dean's own words, right? "My peace is helping people." Isn't that what he's always said? Isn't that what he banked the value of his & Sammy's life on?
Didn't he build his life around keeping Sam safe?Didn't he rightfully assert over & over that's what they're supposed to do, save people together & that's what makes them happiest & gives them meaning? Even with all the sacrifice. That's who they are & he's proud of who they are.
If all of that is true, how can it be in character for him to come to verge of shooting Sam cold? Or saying he'll trade every person they've ever saved just to kill Chuck? Being willing to do those things is incompatible with everything else I've said here.
Counterpoint: nuh uh.
Counterpoint: nuh uh.
I think about Dean's POV here the same way I think about how crushed I have felt as a viewer by every minute of this season & y'all, it works. Not my coolest brag, but I have sobbed real tears & yelled at the screen a thousand times: "then what was the point?" What was the point?
I sunk a decade of my life into loving these characters & taking real pride in the fact that they are heroes & all this season has done is invalidate every victory I ever cherished. Every time they suffered for each other or did something huge for their world...who cares anymore?
In the final fucking season they decided to make it so that Sam & Dean didn't do anything special in Swan Song or any of those other moments along the way. They were just doing what this loser God decided they would do. Holy fuck that's been painful & I'm not the one living it.
Dean has given everything to this purpose of saving people. Even worse, his brother gave everything, too. Isn't he the one who trained Sam into it & brought Sam back in? Every time he passed up a life he wanted, every loved one they lost, Sam's normal & safe...what was the point?
They have suffered so much. They have given up so much. & it was fine with Dean because they helped people & that's what mattered. Until it didn't. If the world can end when Chuck snaps, why suffer so much to save it? If people are marionettes, what's accomplished by saving them?
Chuck took from Dean what Dabb took from us. The ability to care about any of it. Of course he's willing to sacrifice people they saved to get revenge on person who invalidated saving them at all. Wouldn't you steal from Dabb what he took when he invalidated Sam & Dean? I would.
Dean wasn't saying he'd trade all those people for Chuck because he didn't care about them. He & Sam respond to things differently--that's always been what's interesting about them & why Sam vs. Dean arguments are usually trite garbage. Sam's just caring about people differently.
Dean's reaction isn't because he cares less. It's because it's all he cared about & this sonofabitch made it impossible to care. It's because saving them, protecting Sam, these things no longer have meaning.& thus only way to honor them at all is to punish the person responsible.
Now, ultimately be backs down because Sam reminds him there is a deeper meaning that Chuck can't take from them, but it wasn't easy to get there because there is so little left here to feel that for. Sam tries to bring Dean back by reminding him they save people, Dean's priority.
But look at the examples he has on hand: Jack, Eileen, the wrong Bobby, the wrong Charlie. Dean has not made meaningful connections with these people. They mostly just serve as reminders of people he did truly care for & watched die horribly to save a world that is meaningless.
Then Sam brings it back to the one specific Dean can still see meaning in. The only goddamn thing the show still has. "What about me?" Sam. Protecting Sam. Sam & Dean together. That's what reaches Dean because that's only thing the current canon has still not managed to devalue.
Listen, it's easy to joke about how desperate I've been for good brothers content & how I'll take anything, but that's not why this scene worked for me. A few seasons back, there was a scene where Sam said almost identical stuff to Dean when he thought he was going to die.
Now I can buy that when he thinks he's dying Sam will default into babbling about how much he loves his big brother who did everything for him 
uwu. But it came out of nowhere in the ep & fell totally flat. Nice, empty words. Unearned payoff. This time it was genuinely earned.
uwu. But it came out of nowhere in the ep & fell totally flat. Nice, empty words. Unearned payoff. This time it was genuinely earned.
I see, for the first time since they killed off Dean's Michael storyline last season, potential in this show's evolving mytharc. Do I think they are going to deliver on it? Probably not, let's be real. But I'll give credit to the episode for giving me the glimmer of possibility.
Unfortunately, they now set up a situation where there is a possibility for one & only one meaningful & satisfying end for these characters. I've always been Team Blaze of Glory. Sorry to announce I can no longer dream of that sweet sweet Thelma & Louise Impala drive off a cliff.
But if they make it out, kill Chuck & get freedom, & then live with that for some amount of time? Invalidation of S15 will still not be best way it could have gone, but it will at least have gained purpose. Only that ending. Sam & Dean. Alive. Choosing to save people. Together.
