Going in a slightly different direction, the two saddest films I have ever seen are 火垂るの墓 / Grave of the Fireflies (1988 - Ghibli - Japan) and Hiss Dokhtarha Faryad Nemizanad / Hush! Girls Don't Scream (2013 - Iran). In both of them you can feel the exact moment when the protagonist loses hope and it really hits you.
Both of them deserve a pretty strong warning--I guess the second one more of a true "trigger warning" and the first just a warning of how sad it is. You cannot get them out of your head after you have seen them.
Grave of the Fireflies is a devastating and a timeless tail. Even the most jaded viewer, immune both to sentimental schmaltz and posturing brutality in cinema, finds their resistance slipping away as they watch. Many cite it as one of the most beautiful and devastating films they’ve seen, and it has become something of a cliché to say it’s a film you cherish and never want to see a second time because of its impact.
I saw this as a teenager and never have I sobbed as hard as I did watching a movie. It was devastating and I too will never watch it again, even though it's a beautiful movie.
In contrast, I must have watched "Spirited Away" at least 50 times and have gifted it as present to the young ones in my extended family. Not only is the animation compelling but so is the story, the characters and the soundtrack. It's a message about resilience and adaptability and encompasses the spiritual and the fantastical.
Prior to this, I was relatively meh after hearing about the aggression towards civilians till I saw this "kids" movie. In India, they taught us the atom bombs were the biggest tragedy on humanity but I learned of something worse inflicted in next order of magnitude.
Grave of the Fireflies I'm calling the most sad anime ever. It is indeed a wonderful movie. I had a friend say "oh have you ever seen that really depressing anime?" and I immediately said "Grave of the Fireflies?" Nailed it!
An ex showed me this movie and I was actively hostile afterwards because I wasn't given a heads-up on how depressing it was going to be and I hadn't prepared thinking it was just another cute Ghibli film
I bought Grave of the Fireflies when it was first released on DVD and expected it be something I'd watch over and over again, why else buy the DVD right?
Nope. Saw it once, cried my eyes out and it sits cherished on my shelf, never watched a second time.
Both of them deserve a pretty strong warning--I guess the second one more of a true "trigger warning" and the first just a warning of how sad it is. You cannot get them out of your head after you have seen them.