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
Obtain an A-Rank or higher on all bosses in Inkwell Isle II
Complete the game on Expert
Obtain an A-Rank or higher on all bosses in Inkwell Isle I
Obtain an A-Rank or higher on all bosses in Inkwell Hell
Defeat a boss with an Extra Special move
Buy everything in Porkrind's Shop
Get every coin in the game
Complete all levels without killing an enemy
Get an S-Rank
Complete a level without getting hit
Defeat a boss using only the mini-plane bullets
Complete the game on Normal
Defeat the Devil
Give in to the Devil
Complete the Casino
Parry five times before hitting the ground
Defeat every boss in Inkwell Isle III
Get every coin in all of the levels
Obtain all Super Arts
Defeat every boss in Inkwell Isle II
Defeat a boss with a Super Art
Defeat every boss in Inkwell Isle I
Complete 100 parries
Find a shortcut
Defeat a boss
Complete 20 parries
Get an S-Rank on a stage of Inkwell Isle IV
Defeat the King's Gauntlet
Have 9HP at one time
Obtain an A-Rank or Higher on all bosses in Inkwell Isle IV
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 10 bosses with Ms. Chalice
Complete your quest on Inkwell Isle IV
Defeat every boss in Inkwell Isle IV
Defeat all of the King of Games' Champions
Defeat a boss with Ms. Chalice
Defeat a boss with one of Porkrind's new weapons