Dean wasn't entirely sure where he'd heard the line (probably one of geek-boy's lame-ass references to something he'd read or watched), but he did know it was one one of the stupidest things he'd ever heard.
"This is how the world ends: not with a bang, but a whimper."
Dean Winchester, not only one of the instigators of the Apocalypse (after all, he had broken the first Seal) but who also bore witness to it each day, called complete and utter bullshit.
The world wasn't ending quietly. It was ending with screams and terror and death as the streets were bathed with blood, both human and demon and whatever other nasties lurked in the blanketing darkness. In short, this mother was going out with a bang that put Casa Erotica XIV to shame; there was nothing quiet about the damned thing.
However, when Dean slumped against the Impala, face swollen and eyes barely open as he watched the blurry form of Sam taking control from Lucifer, he didn't hear the loud noises of the Cage being re-opened, or Michael-a-la-Adam's enraged scream when the angel realised Lucifer-a-la-Sam was headed back to the Pit - alive. He only heard Sammy's whimper as the two brothers fell into the open Cage, the ground sealing up behind them. Dean's world ended as his baby brother's whimper rang in his ears.