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