Here is the full list of all 18 Blackwell Deception achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Finish the game in commentary mode
Complete the game once
Come back from the void
Free Rosa
Not bad, for a dead guy
Use Rosa's business card for an unintended purpose
Use Joey's breath ability on at least 10 people
Find Jamie's favorite song
Find a lost item
Visit another psychic
Get out of a sticky situation
Sometimes you've gotta rob a few old ladies...
Abuse an innocent
Find all the references to previous games in Rosa's apartment
Save a ghost... and yourself
Escape the yacht with only getting shot once
Open the secret compartment on the first try
Use both Rosa and Joey to solve a puzzle