What is most horrifying is that Lucifer loves him, as Lucifer's by right of victory, as the brother Michael is not, as Sam's soulmate. He welcomes Dean's presence when he wins, or Sam does, smile on his face so familiar Dean could sketch it from memory but he can't tell who's wearing it and doesn't want to. Humanity burns, and Dean is setting off fireworks with the devil in his brother's body, mockery or memory or both, and despite it all, he knows he'd still choose this over fighting, every time.