This trophy will require you to play through Armageddon at least four times. The reason for this is that some scenes will require you to have played the boss fight as different characters. The order you should approach Armageddon is thus:
--First run--
Chapter 1: Cornelius
Chapter 2: Oswald
Chapter 3: Mercedes
Chapter 4: Velvet
Chapter 5: Gwendolyn
*This will unlock the Normal Ending and the Wheel of Fate book.
--Second run--
Chapter 1: Mercedes
Chapter 2: Cornelius
Chapter 3: Oswald
Chapter 4: Gwendolyn
Chapter 5: Velvet
--Third run--
Chapter 1: Velvet
Chapter 2: Mercedes
Chapter 3: Gwendolyn
*Once you've made it to Chapter 4, retreat to the Attic and read the Wheel of Fate book. Save after skipping the ending, and then resume. Armageddon should have reset from there.
--Fourth run--
Chapter 1: Gwendolyn or Oswald
Chapter 2: (Anyone but Cornelius/Velvet)
Chapter 3: Cornelius or Velvet
*Same deal as before. Reset with the Wheel of Fate, only it will prompt you to view the complete ending. If it does not prompt it, you have missed one of the pairings and might need to play through Armageddon to meet one of the pairings mentioned before. In it, Cornelius and Velvet have collected the last Valentine coin (from Alice) and use it to break the curse of the Pooka. The credits are lengthier in respect of this ending, too.