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.
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.
Play a perfect game of beer pong.
Reunite Milo and Lola.
Play as Lola after fighting with Milo.
Intentionally curse twenty times.
Get Apollyon's Seal of Approval.
Try 20 different drink types.
Reunite Beth and Asmodeus.
Get Asmodeus's Seal of Approval.
Drink a lot of booze.
Pet the damn dog.
Get an Invite to Satan's from Fela.
Play a perfect stacking game.
Kick off your adventure in Hell.
Waste 20 minutes on Bicker.