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