Here is the full list of all 11 Neversong achievements.
Beat the entire game without getting hit!
Beat the entire game in under 1 hour!
Beat the game twice!
Beat Skunky's Granny in less than 5 minutes!
Collect all Coma Cards!
Enter all the secret rooms with the Gemstone Key!
Cheat by playing songs out of order.
Beat the entire game without dying!
Beat Dr. Smile in less than 5 minutes!
Beat Jon's Dad in less than 5 minutes!
Beat Simeon's Mother in less than 5 minutes!