The bad ending is unique compared to the others because of the ways it can be obtained. Rather than there being one set path towards this ending, the game keeps track of every time you get yelled at by an authority figure in the castle(Conrad, Reva and Aydin); press your luck too much and you'll be sent to your father, the King, and complete the bad ending. Please note that this is the only time you'll see inside the King’s room.
The following actions count towards the bad ending:
If you get yelled at and aren't aiming for the Bad Ending, you can give an apple to Madam Appleby to reduce the counter. Apples can be obtained infinitely from a crate in the Kitchen or Training Grounds. You can only carry one apple at a time.
The variation to the bad end is by far the easiest ending in the game; however, obtaining the ending this way does not include the conversation with the King. If you look at Monica's study books on her desk in the room with Appleby at any point in the game and select "Yes, I'm sorry I troubled you earlier." You will then go back to your studies and trigger the Bad Ending.