Here is the full list of all 11 The Grand Ball achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
All Endings
Declined Jameson's assistance
Ended with the Duchess of Cumberland
Reached the end and shook hands with Alfred
Romantic Ending with Eliza
Caught with Earl of Doncaster.
Opted to help the Margrave
Took it on yourself to seal the leak
Went on the crazy night hunt
Romantic Ending with Christine
Arrived at the ball.