Season 5 episode 22 - Swan Song
It’s okay, Dean, it’s gonna be okay. I’ve got him.
For Dean, this is it, their clock’s run out. Because Sam isn’t going to walk off this field, and therefore neither will he. He makes the choice, though there was never an option in his mind, to walk right in the middle of the armageddon’s ground zero. Because he won’t let Sam die alone. If Sam is going to die and he can’t stop it, he’ll die by his side. So even though his face is pummeled into oblivion and he just watched everyone else he cares about die, he calls out to Sam to let him know that it’s okay. Because he’s there with him. He won’t ever leave him, even now at the end of everything.
And for Sam, who has been kicking and screaming this whole time, doing everything his incredibly strong mind and soul can do to try to take back control and stop Lucifer, it’s literally the power of love that saves them. Saves everyone. The sun reflects off of the Impala and catches Lucifer’s eye for a moment, bringing into view the toy soldier Sam jammed into the ashtray as a child. And it opens a floodgate of memories for Sam, starting from that point and on, forever by his brother’s side. Memories of the past five years with Dean, riding shotgun and listening to the same 5 tapes over and over again. Laughter and tears, life-changing moments and little pleasures, hunting evil and being hunted by the police, prank wars and singing off-key, all leading up to the moment when his brother sold his soul for him and hugged him so tightly that it hurt.
Lucifer’s endless centuries of planning and stewing in the pit, as well as God-ordained prophecy and destiny, was completely undone by one thing that would seem so small in the grand picture of things. Something they overlooked, underestimated, didn’t even remotely care about.
Destiny itself was undone by the love between Sam and Dean Winchester.