Here is the full list of all 23 FlipWitch - Forbidden Sex Hex achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Defeat the Chaos Witch
Complete all Chaos Events
Collect all Gachas
Defeat the Sphynx Sub Boss
Collect all Costumes
Defeat the Frog Boss
Defeat the Tako Queen Sub Boss
Defeat the Plague Sub Boss
Defeat the Slime Boss
Defeat the Slime Sub Boss
Defeat the Mushroom Sub Boss
Enter the VIP Room
Defeat the Angel Cloud Sub Boss
Defeat the Angel Boss
Defeat the Harpy Crow Sub Boss
Defeat Demon Boss
Defeat the Demon Sub Boss
Defeat the Ghost Sub Boss
Enter the Cabaret Cafe
Defeat Ghost Boss
Defeat the Goblin Ex Boyfriend Sub Boss
Defeat the Goblin Queen
Defeat the Fairy Boss