Here is the full list of all 28 Serial Cleaner achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Complete all movie-themed bonus contracts
Find all secret items
Unlock all costumes
Complete any night-time contract 20 times
Play all Challenge modes
Clean 100% of blood in all story contracts
Complete all story contracts
Complete any daytime contract 20 times
Dispose of 150 bodies
Get killed by a Shooter for the first time
Slide on blood for a total of 45 seconds in any single contract
Talk to Mom 15 times
Read a newspaper 15 times
Watch TV 15 times
Listen to the radio 15 times
Use a shortcut to escape an enemy and then get caught by an enemy at the other side
Make an enemy react to a missing item or body bag 100 times
Get at least four enemies to investigate a sound decoy
Be pursued by at least three enemies simultaneously
Hide while in view of an enemy five times durin any single contract
Use Cleaner Sense for a total of at least 10 minutes
Check out any Challenge mode
Clean 100% of blood in any contract
Play a contract wearing an unlockable costume
Escape capture five times in any single contract
Be pursued by an enemy for five seconds
Fail a contract five times during a single playthrough
Find your first secret item