This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Eight Crazy Nights
In the film, Adam Sandler's character is an asshole to everybody, even the kindly-yet-eccentric guy who takes him in. Then it's revealed the reason for his behavior is that when he was 12, his parents were killed in a car accident on their way to his basketball game during the winter holidays.
Even worse was, after the Intervention song, his reading the note in the empty mall, hearing it in his parents' voices He breaks down in tears, pictured above.