There are 5 official endings and one extra game over ending (not sure this one counts, but if you didnt get it yet, then worth a try)
Ending 1: Good ending. Complete the shift successfully.
Ending 2: Standard ending. Also complete normal shift.
Ending 3: Bad Ending. Dont put the mark while burning the demon.
Ending 4: Basement Ending. If you havent had the basement event yet you will be missing the combination to the safe where the key is stored. You will have to play until an illusion of a basement appears in the Fridge Room. From the demons you will get the combination 6 digits and remember the order. You can use this in the small key safe inside the cabinet next to the Tubing. As long as you continue playing the same game (any shift after) the combination will be the same and you can keep trying if you fail.
Once you have this key, just go to the basement outside, explore it, and make sure to chat with the person under the second door (use the old key from the drawers under the srap of paper).
Then complete the game by burning the correct demon.
Ending 5.1: Make sure to take the coins from Rebecca's apartment before going to your shift. Then hope for the event where Rebecca appears hanging herself in the corridor on the way to the Fridge Room. Place the coins in her hands. Then, just fininsh the shift burning the correct demon.
Ending 5.2: There is also a second way to get this ending. Dont forget to take Rebecca's Dad's necklace from the apartment before the shift. When the corpse on the table changes to your dad, then you will be able to place the necklace on him and this will trigger Ending 5 when finished correctly.
Game Over Ending is by burning the wrong body. Just start the shift and go ahead and burn any body. This should be enough (unless you are unlucky to burn the demons body without the Mark which will trigger Ending 3.