Here is the full list of all 23 Afterparty achievements.
Fail to beat Satan.
Intentionally lose to Satan.
Recruit the Drunk Idiot Demon for Satan's final challenge.
Play as Lola after fighting with Milo.
Pet the damn dog.
Get an Invite to Satan's from Fela.
Beat Satan and earn your way back home.
Make friends with Sam.
Make friends with Wormhorn.
Play a perfect game of beer pong.
Reunite Milo and Lola.
Play as Milo after fighting with Lola.
Get Apollyon's Seal of Approval.
Play a perfect stacking game.
Reunite Beth and Asmodeus.
Get Asmodeus's Seal of Approval.
Waste 20 minutes on Bicker.
Drink a lot of booze.
Get an Invite to Satan's from Lynda.
Don't miss a step while dancing.
Intentionally curse twenty times.
Kick off your adventure in Hell.
Try 20 different drink types.