Here is the full list of all 23 Afterparty achievements.
Intentionally lose to Satan.
Drink a lot of booze.
Make friends with Sam.
Reunite Milo and Lola.
Intentionally curse twenty times.
Play as Milo after fighting with Lola.
Get Apollyon's Seal of Approval.
Waste 20 minutes on Bicker.
Get Asmodeus's Seal of Approval.
Pet the damn dog.
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.
Fail to beat Satan.
Beat Satan and earn your way back home.
Make friends with Wormhorn.
Recruit the Drunk Idiot Demon for Satan's final challenge.
Reunite Beth and Asmodeus.
Play a perfect game of beer pong.
Play a perfect stacking game.
Try 20 different drink types.