The Teenage Mutant Ninja Turtles have had more iterations than most fans could even count across comic books, live-action adaptations and a myriad of animated series. With so many different versions of their story, it's hard to imagine that many things could stay the same across every single one.
Of course, the Turtles' father and mentor, Hamato Yoshi aka Splinter, has always been there for the Heroes in a Half-Shell. At least, he's been there as long as he could be, as the fan-favorite character has met his end more than once across in both cartoons and comics, and each time has been worse than the last.
Requiem
The Hamato Yoshi of the 2012 Teenage Mutant Ninja Turtles television series had a life much like the previous versions of the character, acting as a loving father and patient teacher to the titular heroes. And, much like the previous versions of the story, Splinter and the Turtles found themselves frequently facing off against Shredder and the Foot Clan. During the Triceraton invasion early on in the series, Splinter was murdered by the Shredder. Luckily, this death would be undone with some carefully calculated time travel. Unfortunately, during the episode "Requiem" in the fourth season of the series, Splinter was once again killed by the upgraded Super Shredder in a vicious attack that shocked the team to their core. This Splinter would continue to watch over his clan as a spirit, but that never took away the sting of his loss.
TMNT #100
2019's Teenage Mutant Ninja Turtles #100 by Kevin Eastman, Tom Waltz and Dave Wachter saw the "City at War" storyline finally come to an end in the worst way possible. With the skies of New York City being torn apart by an ancient dragon and the streets filled with demonic entities, the Splinter Clan is fighting a losing battle to buy time for their mentor to save the world. Splinter, in deep meditation, makes contact with the spirit of none other than the Shredder himself, Oroku Saki.
In a last-ditch effort to restore balance to the universe and the mystic forces that have threatened to plunge it into darkness, Splinter sacrifices his own life, giving Oroku Saki another chance to redeem himself by putting the dragon and its master's reign of terror to rest. While this loss hasn't brought the peace those who witnessed it may have hoped for, it did give them another chance to set things right and end the war that had enveloped their lives for years.
The Last Ronin
The future of The Last Ronin is easily the darkest future that the Teenage Mutant Ninja Turtles have ever seen. On the night that April O'Neil accepted Casey Jones' marriage proposal, with their dinner table set and as they waited for their friends to arrive, the scene couldn't have been more ideal. Unfortunately, the Turtles came into their home not in joy, but in horror as they swept the food to the floor to make room for their master. An ambush by the Foot had left Splinter with more wounds than any of them could count. This, the most heartbreaking death of Splinter so far, only led to further loss when Raphael went to avenge his dying father and ended up trading lethal blows with Karai.