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