Here is all the caracters you need to kill to unlock this achievement.
Operation II:
- The guard with 10 coffees (reference the Coffee's for Cleaners achievement)
Operation V:
- The dog with the bulldozer (reference the Monster achievement)
Operation VI:
- The police officer with the gun from the cabin
Operation VII:
- The woman at the caveman exhibit with the spear you get from the body.
Operation VIII:
- The office guy by overdose (reference Don't Get High On Your Own Supply achievement) or the knife from the body.
Operation IX:
- The security guard with the knife from the house.
Operation X:
First you need to pick the letter opener on the blue boxe, inside the locked office room and use it on:
1. The receptionnist
2. The andry drivers after the car accident
3. The surgeon after you unlock the door with the screwdriver
Full walkthrough of Nobodies: Murder Cleaner with no evidence left behind: