Here is the full list of all 20 Gore Doctor achievements.
Complete the Awakening location.
Complete the Sanctum of Madness location.
Complete the Monstrous Mindscape location.
Complete the Adrenochrome Abyss location.
Complete the A Will to Survive location.
Complete the Descent into Insanity location.
Complete the Chamber of Bones location.
Complete the Showdown in the Abyss location.
Complete the game.
Defeat the Kitchen Lady.
Defeat the Crazy Clown.
Deafeat Doctor Gorberg.
Slice the prisoner with automatic saws.
Execute the prisoner on the electric chair.
Chop the head of the prisoner.
Solve the piano puzzle.
Solve the candles puzzle.
Solve the specimen jars puzzle.
Fill the chalice with blood.
Solve the discs puzzle.