Absolution...
...Steamcraft
Castiel's hands clench and release on the pistol's trigger repeatedly, flesh and blood splattering the walls. This is it, he thinks without bitterness or regret. This is how he dies.
He's not stupid. None of them are. They're decoys for the infected. He isn't raging at Dean on the inside, nor is he wishing for a different outcome.
This morning Castiel blew a shotgun at Dean, and the man leaned into it, inhaling slowly. If Dean had been sober, and Castiel not smoking, then it could have been like old times. The times when they (Castiel, mostly) invaded personal space when learning about social acceptances, or just to give reassurances. Castiel had titled his head to the side, eyes glancing across Dean's face. He didn't dare ask but just tentatively brushed his lips against his friend's lightly and only for a second. The solider didn't move but maybe his jaw tightened a little, Castiel had thought.
"I forgive you," Castiel had whispered. Dean nodded curtly and left after that.
So no, Castiel doesn't hate Dean for his sacrifice. He doesn't even pity him, because it has to be done. He isn't wishing he stayed behind or have Dean fail against Lucifer, even though its inevitable. Castiel knows this was a hard decision on Dean, had seen the flicker of guilt of sending his friends to the Croats.
He's going to stand and fight a loss cause, and nothing else is driving Castiel onward but the hope that Dean will forgive himself before he dies.