Hamegg's death in the original manga. Despite everything he did his last moments are crying out that he will never see his daughter again.
Hamegg: This will be my end.. I wish I could see Merry- Oh, Merry! Save her.
The ending for the manga and the 1997 movie: After watching his wife die from the plague and his son run away from home, Kimba/Leo agrees to take part in an expedition to Mt. Moon. He soon becomes blind, starts having nightmares about Rune never returning home, and ends up sacrificing himself to save one of his human friends. He dies without ever knowing if Rune came back home afterwards while his pelt and flesh is used to keep Dr. Mustache alive.
Also in the manga and 1997 movie: after Kitty/Lyra dies, we see Kimba and Lyra's daughter Lukio/Rukio crying next to her body. The next morning, we see her happily laying flowers next to her grave as Kimba/Leo is somberly looking at the clouds. As she continues laying more flowers on to her grave, she suddenly collapses. Kimba quickly runs up to his daughter's body and discovers that Lukio attracted the plague. Kimba is visibly shaking and on the verge of tears. Turns out Lukio quickly caught the same plague as her mother while mourning her death. Thankfully she survives the plague.
The entire scene where we see Kitty/Lyra dying. She's extremely weak, writhing in pain and weakly yells in agony. She's barely able to speak, and requests to have a short conversation with her daughter Lukio. As she's dying, Kimba (alongside Bucky, Pauly, Dan'l Baboon) are sadly watching on and start bowing their heads. According to one anonymous fan, Veronica Taylor (english voice of Lyra/Kitty) actually cried while recording her lines for that scene.
Kimba the White Lion (1965)
Episode 1: Go, White Lion
The 1965 series starts off with Kimba's parents dead, in the first episode!
Episode 2: The Wind in the Desert
The Death of James Brawn, despite the censors of the dub trying to tiptoe around it. It's more heartbreaking in the 1993 dub where he finally gets to be a poet
Episode 3: A Human Friend
Despite being a complete bitch, Mary was genuinely sad when she believed Ranger Roger was killed in the collapse of the stone bridge.
Episode 5: Fair Game
Quasimodo (Bongo/Speedy's grandfather) living in the sewers after escaping. In the original Japanese Dub and 1993 dub he wishes to return to the jungle with Kimba, but is killed by police officers. Kimba has to break the news to Bongo that he saw his grandfather killed.
Episode 24: Gypsy’s Purple Potion
Kimba is tricked into ingesting a poison, which turns him purple and lifeless. Dan'l believing him to be dead lies his body next to Ceasar's pelt and breaks into tears.
Episode 31: City of Gold
A giant turtle helps Kimba, Tom, and Tab escape from a collapsing cave he lived in for ages; the dub's attempt to overlook his death just made the scene tragic in a very relatable way:
Tom : "Poor turtle; he saved our lives..."
Tab: "But lost his home."
Episode 36: The Monster of Petrified Valley
Colloso is the titular monster, who is actually a Brodo Bird. Despite his size and appearance he was quite the Gentle Giant who loved flowers and singing and became Kimba's friend. Despite this his clumsiness and lack of socialization annoyed the other animals, and they decided to drive him out after he tried to eat a hedgehog. In the end he goes back to his original place, during heavy rains against the wishes of Kimba and is killed by a rockslide while Kimba cries his name.
