How to Unlock Leftover Coffins Achievement
This achievement can be done only while being at the cemetery for the first time. If you had exited it already, the only way to get it is to start a new game.
Before exiting the cemetery, there are two men who are guarding gates. Simply take one of the random items that you can move and make them levitate thanks to the “LMB”.
After this, just drag it to the guards. As soon as it is close enough, they get scared and faint. It is enough if only one guard faints.