Third panel, Sam’s face:
Jared does this awesome burst of subtle controlled anger there, like Sam is mad that Dean can’t have faith in him or trust him to save him. Followed by hurt. And then the stubborn kicks in…
I will always have special feelings for Faith, because I came out of it going “….SAM, I FEEL LIKE YOU WOULD HAVE DONE THAT ANYWAY, EVEN IF YOU HAD KNOWN THE CONSEQUENCES. DO YOU HAVE A SECRET STEELY RUTHLESS SIDE HIDDEN UNDER THERE SOMEWHERE?” which I sort of categorised as fanon at the time, but then when Mystery Spot aired and robo!Sam turned up for the first time I immediately went “Hey! Hey it’s you! I recognise you! I caught a very brief glimpse of you in Faith. YOU DO EXIST.”
So for me Sam’s face in the third gif isn’t anger at Dean for not believing him, it’s anger at his own apparent helplessness, and it’s anger that the universe would dare to take Dean away when it had already taken Jess. It’s that anger that allows him to be so confident in the fouth gif. Sam knows he will save Dean, because the idea that he can’t save Dean is too vicious not to tear down anything standing in his way.
aaaaand we’re back to me falling to my knees and shaking my fists at the sky, cursing Kripke for changing his mind and not letting Sam save Dean from Hell. Because it completely invalidates EVERYTHING that was set up in the first two seasons and instead of Sam using his powers to tear open the gates of Hell to bring back his brother, irrevocably turning himself into the Antichrist in the process, instead of Sam fighting to keep a hold of his own humanity — and he gets it back, of course he does, because it was all for Dean, he let himself become The Boy King to save Dean — instead of that, we had fucking Jesse who nobody even fucking remembers because he fucked off to fucking Australia after one fucking episode because the writers couldn’t even be fucking bothered and I just as;dlkfja;ldskhgk descending into a rage spiral help
^^
All of the above

(Source: deadwinchester)