The death of Peridot. After it looks like she manages to escape Kira, he reveals that Killer Queen had touched her just before she left his range. She doesn't realize this and when she see's Steven she's elated that she was able to survive. But it doesn't last long because Killer Queen activates its ability and she explodes. Right in front of Steven and her friends.
Steven and the Gems reaction to Peridot's death. They are all heartbroken at the loss of the friend. Garnet stares at the bubble containing her shattered Gems pieces for the entire night. Pearl accidentally displays a hologram of her friend with her Gemstone and upon realizing what she's doing she breaks down as Garnet tries to console her. Amethyst is destroyed and angry that her friend died to what they believe is a Corrupted Gem and now wants vengeance. Connie and Steven are unable to stop crying and in the latter's case blaming himself for her death as he has nightmares about her constantly exploding the following night. And Lapis destroying the barn where she and Peridot had lived together in just to try and bury her pain.
Steven opening up to Kira Yoshikage, not knowing that he killed Peridot. Kira manipulates Steven into talking about his friend's death, and while he does help him deal with his grief, it's not because he cares even the slightest about him. He gets Steven to open about Peridot's death because he wants to make sure she didn't say anything about him before she died. The same thing Shigechi did just before he died. What makes this so heartbreaking is that Steven genuinely feels like Kira wants to help him because he's a kind man.
Steven calling the Gems out on their treatment of him over the years. During his talk with Kira, he pointed out how the Gems have never once been openly honest with the boy unless they were forced to. He also told him that even though they say they're over their pasts issues, they repeat similar mistakes and commit actions that seem to say otherwise. And to top it all off Kira told Steven that his family didn't love him and that they only loved Rose Quartz. Adding in the fact that Peridot's death is fresh in his mind, when he tells off the Gems he's extremely angry and they can do nothing but listen. After he finishes talking and leaves the beach house with tears in his eyes, the Gems break down and cry.
