While she is Ax-Crazy and unstable, Nu's backstory is genuinely sad, her being experimented on and psychologically broken. Even Ragna feels bad for her. In Ragna and Nu's second fight, he absorbs the rest of her memories and learns the full story in that she was abused and experimented on by amoral and uncaring scientists and that she would have visions of Ragna coming to save her from her nightmares. Ragna goes from feeling sorry for Nu to genuinely wanted to help her.
Ragna becoming Beast-Ragna through Terumi's control and attacking everyone at the Tournament, injuring and killing civilians all while incapable of breaking free from Terumi's control. His friends try to stop him through force, pulling out everything that have on him, to which Beast-Ragna completely wipes the floor with them all. To add more insult to injury, when Penny attempts to fight him, Beast-Ragna shrugs everything fired at him and mercilessly rips Penny in two in front of everyone, including Ruby's eyes which leads to Ruby having a mental breakdown and unleashing her Silver Eyes on Ragna, which you think would work only for it to doing absolutely nothing. Clearly this is one of the most darkest and saddest moments in the story as we all know that Ragna is doing this completely against his will, as a puppet that Terumi controls.
Ragna wants to mend things with his brother Jin. But doesn't know how to do so, because too much time has passed and there's so much bad blood between them due to what happened between them when there were kids.
Cinder announced that a very crucial detail of history has been confirmed to be a lie. Regarding the name of the Black Beast. Making things worse is that a lot of people want Ragna dead because of Cinder's announcement that the Black Beast has returned in the form of Ragna, essentially branding him as some form of an Anti-Christ which nearly everyone wants dead or runs away from in fear.
Ozpin is, like in canon, unsuccessful with transferring the rest of the Fall Maiden's power to Pyrrha, leading to Amber and his death by the hands of Cinder.
Cinder not only has turned most of the world against Ragna, but now has attempted to turn Yang and Weiss against him by using an edited video of Ragna's confrontation with her and editing out the part where she threatens his family if he goes to the authorities or anyone for help. What's sad is, it appears to be working as Yang and Weiss completely abandon trying to pursue Cinder for the moment to confront Ragna for hiding the truth from them. It's also very sad because moments ago Yang was defending Ragna from everyone else, and it also plays into her abandonment issue due to the fact that she and Ragna had a very close friendship. Ragna can only stand there and admit the truth as he realizes that Cinder has more or less succeeded in turning the world against him.
The next chapter makes things even worse for Ragna. He admits to lying to everyone and this leads to Yang becoming so consumed by anger and betrayal that she can't even focus on Cinder anymore. Yang becomes so spiteful that she even reveals to Weiss what Ragna did to Jin in their childhood, a powerful Kick the Dog moment due to Ragna trusting Yang to keep that a secret. Outside of context, Weiss now thinks Ragna is nothing but a abusive brother and monster. It gets worse when Yang agrees to forgive Ragna, but only if she brings in Nu to Ironwood, however Ragna's convictions make him refused to do so because he doesn't trust the General and believes that they'll kill or imprison Nu, who he now sees a a victim of abuse and experimentation and never had the chance to actually have a normal life. This leads to a heartbreaking fight between the three of them, in which Nu awakens and attacks Yang, cutting off her right arm, for thinking she was trying to kill Ragna. Weiss is devastated and becomes fully antagonistic towards Ragna, who can only walk away as Weiss screams at him angrily.
Weiss: Winter was right about you, Ragna. YOU HEAR ME?! WINTER WAS RIGHT ABOUT YOU! YOU DON'T BELONG HERE AT BEACON! Ragna: I suppose you're right, maybe I don't belong here.
Celica's supposed death at the hands of Terumi (granted, there's no confirmation yet but she was hit by a poisoned Ouroboros). Beforehand, Celica was trying to appeal to Emerald and Mercury, sensing that they had suffered a lot of abuse and heartache and tried to convince them that Cinder doesn't care about them. What's worse is that Terumi attacked specifically because she was trying to redeem them. That's right, Terumi is such a monster that he would defuse any attempts at trying to make others perform a Heel–Face Turn. Thankfully she survives but she is now in a coma and both Saya and Ragna are traumatized by what has happened.
Ragna's journey and arrival at the top of Beacon. While this could also qualify as an awesome moment, Ragna cleaving through Grimm effortlessly as his rage boils up inside of him is hard to read given how much stress and pain he has went through. He then arrives at the top of Beacon only to be curbstomped by Terumi who begins to utterly destroy him and Ruby verbally, revealing that everything they knew was a lie and that Nu was Ragna's sister all along. Ragna then finally has his arm cut off by Terumi and barely survives after nearly killing Cinder.
What's even more heartbreaking is that during the scene of his rage boiling up and cleaving through Grimm, he's not just angry but sad, with tears running down his face with him finally crying for possibly the first time in years. Ragna is in pain, from being forced to attack people, losing his best friend and having the closest thing to a mother be almost killed, Ragna has really hit the deep end.
Just the whole state of Ragna and Yang's relationship currently. Ragna feels genuinely guilty for lying to Yang and wants to seek forgiveness and redemption, however Yang is so consumed by anger and misery that she has straight-up disowned him and threatens to make him suffer if they ever cross paths again. Meanwhile Ruby is torn between the two and can't seem to make her mind if she's on Ragna or her sister's side. Unlike in canon where Blake was the one who wronged Yang and simply abandon her, Ragna's actions have straight-up led to her becoming far more toxic and spiteful, and acts far more hostile to Ruby.
Yang's condition is no doubt hard for viewers to stomach. She has become so blinded by rage and sadness that nearly all of her positivity has been replaced by spite. Besides the kiss she has with Makoto, it's clear she is still very depressed and miserable. It gets even worse when she acts far more toxic towards Ruby than in canon, then denounces her faith in the Six Heroes to Jubei and tells the remorseful hero to never come back. The fact that she seems to want to straight up get revenge on Ragna really shows how much she has fallen as a person.
Ruby's worldview being utterly destroyed. First she learned that the history of the world has many lies. For starters, the Kingdoms wanting the Six Heroes dead. Then lying about the names of the Black Beast and the Nox Nyctores. Making things worse is that one of the six heroes is the one who killed her mother. To add insult to injury, Terumi killed Pyrrha the way he killed Summer. While Ruby is still determined to help people, it's tough to see her experience all of this. Especially when you remember that she is still 15 years old.
Jin killing Penny when him and Ruby were fighting her. Despite Penny being mind controlled by Relius, Ruby did the best she could to help her friend before Jin viciously cut her down. Though he did it to save Ruby when she was in danger. The action itself still has a major effect on the young girl.
Both Mai and Tsubaki's secrets being revealed during the party in chapter 63. For Tsubaki's secret, it is implied that she is a child of incest. While Mai's secret of being a transgender was implied further. Though Kagura defended his teammates and stood up to the Trophy Wife and her husband, the damage has been done.
Jin's guilt over not being able to save everyone during the Fall of Beacon.
Team KKMT's, Carl, and the Happy Huntresses reaction to being inside the Murakumo labs. Seeing that people have been experimented on. Which ranges from Men, Women, and children is a sickening sight.
Carl remembering what his father Relius did to his sister. Making things worse is that he wa given a reminder of this from being in the Murakumo Labs.
