Edmund finds young Fanny crying and tries to comfort her. A teenage boy who takes care of his small 10-year-old cousin is a rare sight. Him helping her write a letter to her dearest brother William is especially endearing.
Fanny feeling sorry for Sir Thomas Bertram despite the fact that he verbally abuses her.
The realization that, for all her fault, Mary Crawford does love Edmund.
Fanny refuses to say anything that will hurt her cousins's reputation, despite the fact that she could actually save herself from Mr. Crawford in the second.
Fanny's gradual realization of Susan's merits, and her joy at finding someone else who loves her and whom she can both love and esteem.
Also, Susan being offered residence at Mansfield Park where she finds happiness under the love of Bertrams.
Heart-warming moments from its adaptations
In the 1999 movie, Sir Thomas' recognition that Fanny, not he, has been the Only Sane Man:
Sir Thomas: You read it, Fanny. You have such a strong, clear voice.
In the 1983 miniseries, when Fanny is invited to dinner at the Parsonage. Just after Mrs Norris has delivered yet another lengthy "The Reason You Suck" Speech to Fanny and told her that she'll have to go there on foot, Sir Thomas walks into the room and casually asks when would be convenient for the carriage to come round. When Mrs Norris protests, he states flatly that no niece of his is going to walk to a dinner engagement. In the next scene, Fanny is riding in the carriage with Edmund, with the biggest, happiest smile on her face that she's worn in the series to that point.