- Mr. Bennet having to come back from London without having found Lydia, facing the awful truth that his family may very well be ruined because he refused to put any real effort into being a proper father to his younger daughters. Even when Elizabeth and Jane try to console him, he tells them no - they should allow him to feel the weight of his guilt, because It's All My Fault.
- Elizabeth's Love Epiphany, because it comes with the conviction that they will never be together. Our knowledge of the Foregone Conclusion is no comfort to her. It's hard to see Elizabeth so shattered and depressed because she was so arch, lively, and spirited before.
- In Mr. Bennet's reaction to Elizabeth's engagement to Darcy, he drops the snarky mask and we get a peek of the regret he carries around with him. This line is specially sad.Mr. Bennet: My child, let me not have the grief of seeing you unable to respect your partner in life.
- Lydia's eventual life detailed in the Where Are They Now epilogue is pretty sad, even if she doesn't realise it herself. Her husband soon loses whatever affection he had for her and they're incapable of making a stable home for themselves thanks to their overspending and fickleness, 'always moving from place to place in quest of a cheap situation'. Worse still, although Jane or Elizabeth will grudgingly help with their bills, none of Lydia's family (save probably her mother) can bear to have her or her husband around for long. When they're first married Mr Bennet outright refuses to welcome them at Longbourn until his wife and daughters plead with him to let them stay; while Lydia often invites Kitty to visit her (with promises of balls and young men) Kitty's always forbidden from going; and when the Wickhams go to stay with her older sisters, it's not long before they're getting broad hints to depart. In one 2016 open air production in Regents' Park, there's even a moment where Lydia goes to bid farewell to her father before she sets off as a married woman...and he silently rejects her with a glare. She's left staring at her family in trepidation, her bubble quite burst, before she leaves. It's small wonder that adaptations now often prefer to change Lydia's fate in the story.
Tear Jerker / Pride and Prejudice