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