Kurama's sendoff to the future. It's revealed that there's no hope for him, Naruto and Sakura to defeat Kaguya. Instead Naruto has to send Kurama to the past as Kurama is the only one who could survive the trip. Kurama has to leave watching his Only Friend die, carrying Naruto's hope that he can be a hero.
Kurama waking up in the past alone with the knowledge of everyone he loved is gone.
Young Naruto when Kurama first meets him. Naruto doesn't have anyone in the world, the civilians and children shun him, the shinobi stay away from him due to orders and the Hokage has no time for him. Naruto has nothing to smile about. Kurama decides to change all that.
Kakashi ripping Kurama away from Naruto, who just revealed that they're family. Kurama begs him to let him stay with Naruto only for Kakashi to justifiably refuse. Which sets up a fight that could have been avoided.
When Kurama and Naruto first meet Gaara, he's a murderous Creepy Child who has killed his beloved uncle in self-defense and has a body count. All it takes is a little care and affection from Naruto and Kurama to reveal Gaara as the shy, love-starved child he actually is.
Hell, just a jinchuriki's childhood. Take anyone, you won't find neither sunshine nor daisies.
Naruto thought his parents were criminals because no one wanted to tell him why everyone shunned him.
Gaara had to fend off murder attempts because his father deemed him a failure and he had no other company than a crazy demon inside his head.
Fuu tried to escape Taki. Several times. She was always dragged back kicking and screaming after being beaten for daring to run away.
Yugito was taken away from her parents when she was two years old and relentlessly trained as a perfect weapon, never allowed to take decisions by herself. When she flees Pain and goes find Kurama, that's the first time she chooses what she wants to do.
Han remembers his childhood in Iwa, with a monster in his head and the whole village against him. It was... very lonely.
Roushi lost control of his beast when he first used its power and almost killed his best friend. She was so scared of him afterwards that he could as well have really killed her.
Utakata lived in the Bloody Mist while the graduation tradition was in full swing. Then his father - who wasn't that great to him but still - got murdered by his successor. Also, he doesn't understand why Kurama cares so much about the jinchuriki's happiness.
Kakashi's mind is not a happy place. How did he know that Kurama lost his entire world? Because he sees those dull eyes every day in his mirror.
As Kurama persists to flee and starts to rally others jinchurikis to his cause, Kakashi grows more and more desperate to catch him, refusing to be the second Hatake responsible for a war.
Then he learns Kurama's real identity and almost goes catatonic from shock because the Nine Tailed Fox, a demon responsible for thousands of deaths and destroyed lives is more human and compassionate than him.
Uzu is a shadow of its former self with only a handful of survivors. To make matters even worse, they have been forgotten and their culture is slowly dying out.
Yagura would have been murdered by his best friend because due to no fault of his own, he was mind controlled.
Kakashi Taking the Bullet for Kurama because it was his instinctual reaction to a falling apart cave.
Orochimaru brings Kushina and Sakumo back from the dead to use them as a psychological weapon against Kurama and Kakashi. Sure enough, Kakashi's reaction when he has to fight his mind-controlled father is nothing short of heartwrenching.
Kushina gave her life to protect her baby and ensure he would live long and happy. Then Orochimaru says that everyone in Konoha knew that Naruto was the new jinchuriki to the Kyuubi, and absolutely no one took steps to raise him as a normal kid, letting him growing up on the fringe of Konoha and hated for something he never chose for himself.
Nawaki's death not only deeply hurt his big sister Tsunade, it also outright destroyed his jounin teacher Orochimaru. When the two Sannin find themselves fighting, Tsunade manages to apologize for being so wrapped in her grief she forgot her friend was in pain too.
Hiashi Hyuga takes a few moments to drink and mourn his brother. The fact that he empathizes with the alcohol would be funny if it wasn't depressing.