Full list of all 42 Cuphead achievements. It takes around 15-20 hours to unlock all of the achievements in the base game on Windows.
The base game contains 28 achievements, and there is 1 DLC pack containing 14 achievements.
Obtain an A-Rank or higher on all bosses in Inkwell Isle III
Complete the game on Expert
Obtain an A-Rank or higher on all bosses in Inkwell Isle II
Complete all levels without killing an enemy
Obtain an A-Rank or higher on all bosses in Inkwell Isle I
Get an S-Rank
Buy everything in Porkrind's Shop
Get every coin in the game
Complete the game on Normal
Defeat the Devil
Obtain an A-Rank or higher on all bosses in Inkwell Hell
Give in to the Devil
Complete the Casino
Defeat a boss using only the mini-plane bullets
Defeat every boss in Inkwell Isle III
Get every coin in all of the levels
Defeat a boss with a Super Art
Obtain all Super Arts
Defeat every boss in Inkwell Isle II
Parry five times before hitting the ground
Complete 100 parries
Defeat every boss in Inkwell Isle I
Find a shortcut
Complete 20 parries
Defeat a boss with an Extra Special move
Defeat a boss
Complete a level without getting hit
Get an S-Rank on a stage of Inkwell Isle IV
Have 9HP at one time
Defeat 10 bosses with Ms. Chalice
Defeat the King's Gauntlet
Defeat a boss with one of Ms. Chalice's Super Arts
Defeat a boss on Inkwell Isle IV without killing any of its minions
Defeat all of the King of Games' Champions
Obtain an A-Rank or Higher on all bosses in Inkwell Isle IV
Complete your quest on Inkwell Isle IV
Defeat every boss in Inkwell Isle IV
Defeat a boss with Ms. Chalice
Defeat a boss with one of Porkrind's new weapons