This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Zyuden Sentai Kyoryuger
#2: During Stegotchi's attack, Rika was injured. Nobuharu, as Kyoryu Blue, tried to comfort her, but Yuko shoved him away. It had to hurt Nobuharu who, in his eyes, was responsible for the near death of his niece.
#5: A cut line from this episode had Torin inform the Kyoryugers that all of the Guardian Zyudenchi used to have Zyudenryu forms as well (meaning there were once 24 Zyudenryu), but due to helping the 10 Great Zyudenryu fight the Deboss Army, their bodies were too badly damaged to even gain partners, thus they simply gave Torin their Batteries, and now most of them are now lost, presumably forever, much to Torin's sadness.
#8 talks about dealing with people who have died. The Monster casts illusions of someone deceased that was close to the person's heart and fills them with sorrow. Most specifically, we have Nobuharu's little six-year-old niece, Rika, who is unaffected by this madness. Why? Because she already knows her daddy is dead and is never going to come back but her mother is still affected by the loss. This little girl is able to live her life past a trauma that most grown-ups were unable to do. She's one tough cookie.
Utsusemimaru's past. Oh boy... A monster was about to hurt a child so he protected the kid, but the kid was a mook. The monster was about to kill Utchi but his lord pushed him out of the way and was killed instead. The lord told him that his kindness was his weakness, and then Utchi had to see all of his friends die. Just as Torin was about to be killed, he went into a fit of Unstoppable Rage, making him vulnerable enough to become Dogold's vessel for 400 years. When he finally realizes what's happened in the present time, he's in another fit of rage and disbelief for what he caused. Damn.
Just to make it clear, Utsusemimaru watching his lord die and having the rest of his friends die were separate events. Then to add to all his grief, Pteragordon was greatly damaged and had to rest for hundreds of years to fully repaired. As far as he knew, Torin was the last of his friends still alive and almost watched his execution. Topping it all off, Dogold was gloating about it, telling him it was all part of a plan to claim him and Pteragordon, basically saying that all the deaths were his fault and his body was used for evil. Someone give this man a hug.
And in #25, with the Deboth Monster involving monsters, who does Luckyuro transform himself into? Ucchi's lord, the same one he couldn't save. Compared to everyone else—Luckyuro was Rin for Souji's dream, Amy for Daigo's, Daigo's for Amy, etc.—it was very, very depressing.
#28: Torin is forced to fight against the team, and essentially commits Suicide by Cop so that he doesn't have to hurt them against his will anymore.
#29: In an Imagine Spot, Torin tells the 5 core Kyoryugers his back story. He and Chaos were born in the depths of space to destroy planets, but the brothers were split up as Chaos traveled to the asteroid where Plezuon was whereas Torin was sent to Earth during the time of the dinosaurs. Torin felt a change of heart after witnessing Earth's nature and its dinosaurs and felt guilty that he would destroy something that could have potential to evolve into something wonderful. Ever since then, Torin grew to love the humans and the dinosaurs and has no regrets. Torin bids farewell to the Kyoryugers as he starts to fade away and that Earth is now in their hands.
All 9 Kyoryugers gather around Torin's now stone body and grieve for their fallen mentor, benefactor, and friend.
In hopes of reviving Torin, Daigo and the 4 other core Kyoryugers bring Torin to the Spirit Base. There, they gather stones similar to Daigo's pendant and Ian's treasure and place it on Torin, then they sing a song they learned from the events of the Gaburincho of Music movie. Torin revives to the relief and delight of the 5 Kyoryugers.
After the Deboss have been defeated, Torin gives his thanks to the Kyoryugers, but is unsure if they want him back after his heritage is revealed. The Kyoryugers say otherwise and are happy to welcome Torin back to the team, saying that they will believe in him and they will stop him, should he ever get out of line again. Torin is moved to tears by their words, saying that after billions of years, Earth's beauty has not changed, nor has the brilliance of his friends. All 9 Kyoryugers and Torin walk away happily together once more.
#34: The death of the Guardians, made all the more heart-wrenching when it is revealed that the Guardian Stones are Bragigas's tears, upon seeing his friends dying around him.
#45: Remember what happened in #28-29? It got worse here. Dantetsu has sided with Deboss and killed Torin, petrifying him then crumbling into dust.
Even more, the 6 Kyoryugers are in mourning over this turn of events, Daigo taking it the worst since it's his own father that killed Torin.
Then near the end, Chaos reveals that despite seeing the Legion as his family, he's fully willing to kill Candelira. This causes Aigaron to defect from the group. What's worse is that in a case of Trailers Always Spoil, the preview for the next episode shows that Aigaron possibly dies.
#46: Shows the preview wasn't lying. Even worse is Canderila's reaction, since he'd pushed her out of the way of the attack that killed him.
Never mind that - Icerondo kicks the dog clear across the ocean by telling Aigaron that he was Dead All Along - and then Ian decides to give Aigaron a Mercy Kill...
It gets worse - Ian confesses that he wants to hate Aigaron until the bitter end for what he did to Shiro, breaking down because in the end, he's already forgiven Aigaron. And then Aigaron tries to hand Candelira a flower, trying to get close to her on his knees, and he doesn't make it... Candelira and Luckyuro then break down like a widow and a kid losing a parent.
It gets even worse when you realize Candelira's personality. After all her devotion to smiling and being happy, she finally breaks down in tears and needs someone else to cheer her up again.
Not long after Dogold's death, Uchii dies after commending his friends.
#48: After Ian and Souji fend off the Zourima, they find Nossan holding Uchii's dead body, much to Ian and Souji's horror and sadness. Dantetsu's reaction is none the better when they bring Uchii back to the Spirit Base.
When you really think about it, Torin has an even crappier life than Utsusemimaru. Every encounter he's had with the Deboss was, at best, a Bittersweet Ending. Let's reflect on the encounters he's had with them that we know of...
100,000,000-65,000,000 years ago: Torin and Chaos are created by Deboss to travel across the stars and wreak havoc. As Torin arrives on Earth, he is overwhelmed by the beauty of the planet and the potential for greatness from the dinosaurs. It was at that moment he decided that he would suppress all his violent urges and protect all life on Earth instead. Deboss and Chaos arrive so Torin assembles the Zyudenryu to defend the Earth. Deboss and Chaos are defeated but results in the extinction of the dinosaurs, the death of half the Zyudenryu (which resulted in the Guardian Beast Batteries), the sealing of Bragigas underground and the start of the ice age. Torin is critically wounded and unable to fight at the best of his abilities ever again, and only the power of the dinosaur spirits keeps him alive.
1500 years ago: Deboss rises again, they are defeated once again, but at the cost of Tessai's life.
500 years ago: Deboss rises again, they are defeated once again, but at the cost of Ramirez's life.
400 years ago: Pteragordon is damaged to the point that he has to rest in a volcano for hundreds of years. The army he allied himself with is all but completely wiped out by Deboss, including their lord. Torin is captured and about to be executed before Utsusemimaru charges in and is sealed inside the body of Dogold due to his own rage regarding the situation, but Torin believes him to be dead. Torin takes this one especially personal, blaming himself for the tragedy.
And in the modern day, after he finally has a group of friends he clearly treasures and trusts with his life? All the above is made even worse with the revelation that he too was born of Deboss and is Chaos' brother, having betrayed all that so he could do the right thing and save the very planet he was created to destroy. Chaos and Endolf control him into fighting for them again, reveal the truth of what he is to the Kyoryuger - a fact that Torin is clearly ashamed of to this day - and he ends up impaling himself on Kyoryuzin's blade so he doesn't have to fight his friends anymore. Move over, Ankh, tokusatsu has a new most tragic birdman.
All of the above makes his debut as Kyoryu Silver all the happier. He's realized that he isn't defined by his birth and once more declares his bravery as his light shines once more for the world to see as The Shining Brave.
...And then it went to hell again. Torin ultimately ended up killed by Dantetsu, his close friend and confidant, as well as the only person who can kill him and prevent his return as a spirit. You can hear the pain in his voice as he realizes that he's done for, and this time, bringing him back to life might be impossible.
...And back to the Bittersweet Ending once again. It was revealed that this was the plan; Torin would die so that he would wipe out all monsters in hell while Dantetsu takes his place as Kyoryu Silver. While his death is permanent, he is finally free from his 100,000,000 year struggle against his own kind, the beauty he sought to protect is in the hands of the comrades that he forged an eternal bond with, and is at liberty to finally rest in peace.
Think that Candelila and Nobuharu is gonna end Happily Ever After? Nope. The V-Cinema is going to showcase the descendants of our Kyoryugers, including Nobuharu's. This means that in a few decades, Nobuharu will die and Candelila will be The Mentor of his great-grandson and be all alone again.
Well, this would wind up happening anyway, considering that, being born of Deboss, she has a much longer lifespan than any human (Torin could attest to that). What really makes their situation sad is that she chose to stay away from Nossan, despite giving him some comfort while he thought Daigo was dead in return for him comforting her as she grieved for Aigaron. Since we're not sure whether they will cross paths again down the line, you could as well say they've become Star-Crossed Lovers.
It's worse, it's mentioned that the new blue is Rika's descendant not Nossan's. Implying he never had children of his own...