Here is the full list of all 24 Rhythm Doctor achievements.
Earn an S-Rank on Level 1-XN.
Earn an S-Rank on Level 4-1N.
Earn an S-Rank on Level 2-3N.
Earn an S-Rank on Level 4-1.
Earn an S-Rank on Level 3-X.
Earn an S-Rank on Level 3-1.
Earn an S-Rank on Level 2-X.
Earn an S-Rank in Beans Hopper.
Earn an S-Rank on Level 2-3.
Earn an S-Rank on Level 2-2.
Earn an S-Rank on Level 1-X.
Earn an S-Rank on Level 1-2.
Complete any level in 2-Player Mode.
Enter the "Rhythm Dogtor" code.
Give Dr Edega a headache in the Level Select menu.
Get scolded by Dr Edega in the Level Select menu.
Receive a Score of 0 in Beans Hopper.
Complete the Muse Dash Collaboration.
Save the Insomniac patient and watch the game's credits.
Complete Act 4.
Complete Act 3.
Earn an S-Rank.
Complete Act 2.
Complete Act 1.