This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Mansfield Park
No wonder Mansfield Park makes critics beg for the typical "bright and sparkling" Austen. If the description of Fanny's eight years of deprivation from love and affection don't make you close the book in tears, try to get through any scene where Mrs. Norris Breaking Speeches her, or the scene where she sits in the East Room having a breakdown over the loneliness and sense of zero self-worth that's built up over her life.
The scene at Mr. Rushworth's estate, where everyone keeps more or less abandoning Fanny in the woods (even Edmund, normally so attentive, actually forgets she's there), is really hard to read. It's especially painful since some of the characters make it clear that they're not particularly pleased with her for being where she is.
Sir Thomas, who had been noticeably kind and attentive to Fanny since his return from Antigua, absolutely lights into her for turning down Henry Crawford's proposal without even attempting to understand why she wouldn't want him. And having driven her to tears, he sternly orders her to pull herself together already and try to behave rationally. Fanny, being Fanny, considers that he's right in the latter and wonders if she really is being horrible and ungrateful even with all of her objections to Crawford's character.