This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / My Neighbor Totoro
The scene where calm, level-headed Satsuki breaks down sobbing and asking what she'll do if her mother die. Seeing Mei lost and crying for her sister is no emotional picnic, either.
The knowledge that they never see Totoro again after the end of the movie is bittersweet to the taste.
This scene will definitely cause any younger siblings in the audience to cry buckets. Satsuki says to Mei, "Do you want her to DIE?!" And Mai just keeps screaming "NO!" in protest at everything that is happening, because she is young and doesn't know how to deal with her feelings well. Satsuki looks sternly at Mei and yells, "You dummy! I'm not talking to you anymore!"English-dubbed versions "Don't be dumb, Mei! Oh, I give up. You're so stupid!" ('93) "You're such a baby! Grow up!" ('06) After a few minutes of stunned silence, a soft, high-pitched whimper rises up from Mei and then gradually gets louder as she starts to full-on bawl and wail, saying, "Sis is a dummy!"English-dubbed versions "I'm not stupid." ('93) "You're so mean!" ('06) in the most heartbroken and hurt voice. As she does this, she very slowly trudges after Satsuki, her feet despairingly dragging in the dirt, her shoulders slumped, her head facing down. It's a minor example compared to the others, but Mei is a very young girl, and this scene can hit a nerve with viewers who were treated this way by their older siblings.
Also the way Kanta looks at Mei in this scene. He looks concerned, but he doesn't really know what to do. He just says, "Come on, Mei," and walks slowly with her.
When Satsuki is looking for Mai and she's terrified. You can feel how scared this 11-years-old little girl is, and you can't help crying with her.
When Kanta tells Satsuki that they found a sandal in the pond, and she runs herself nearly to total exhaustion to get there.
The scene of little Mei sitting, exhausted and all alone, by the Jizu statues with the ear of corn in her hand. It's clear that she's been crying. Then when she suddenly hears her sister's voice, she screams/wails "Satsuki?! Where ARE YOU?!" in the most heartbreaking voice.
Basically any time Mei cries, especially in the English Disney dub, where she is voiced by an actual little girl. Whenever she cries, her crying sounds alarmingly realistic - and it's common knowledge that most people are uncomfortable at the sound of young children and babies crying. To add to this, it is NOT a cute cry. She full on wails with her face contorted in pain, her entire face leaking. Every time she cries it feels like a very hard punch to the heart.