This achievement can be found in level 2 "Toxic Love"
At the start of the level walk into the main room and turn left. Interact with the large white painting and go inside the security room. Once inside turn on the power (square with red light on it). Once this turns green go back into the main room and turn right. Go in straight into the kitchen and pick up the toaster next to the microwave.
Once in hand go back to the main room and up the stairs, cross the bridge & open the door on the left. You will find a body in the bath and bloody water. Make sure the toaster is full submerged in the bath water and your achievement will unlock.
Video guide, starts - 1:08