This is one of the final ending achievements, so, spoiler alert.
At the end, you finally get to play your drinking games against Satan. The beer pong phase doesn't matter... win, lose, whatever. Eventually Satan gets fed up and transports himself, along with Milo and Lola, to some sort of extraplanar space to have the final showdown.
To get this achievement, you have to play the stacking game (not refuse on the grounds of Satan being a Hellcoholic), but lose. Just keep missing the stack on purpose.
Satan will give you a couple of tries... after you lose the first round, your other character will get to play, and when you lose that one, he'll offer to let you keep trying, because he wants you to win. Instead, select the speech option "We'll take the loss." The achievement will pop while the story wraps up from there.