When Marie becomes Mesomeso and brutally kills Kanamori.Hedeserved it.
Higanbana unexpectedly putting Sumire in her place when she kills all the bullies Sumire created in Yukari's class. Higanbana smugly thanks Sumire for the meal afterwards.
In "A Thistle of Vengeance," Yukari decides to Take a Third Option when dealing with Sumire and Azami. Instead of using the thistle to become a cruel bully or let herself be bullied, she uses her new power to take control of the classroom and stamp out any bullying she sees.
Nafumi's fate. When it looks like she's gotten the best of Renoir and Higanbana, Nafumi is suddenly reminded of something she said earlier. When she was asked about Yuki's death, she basically said who could figure out why senseless accidents happen? Only... Nafumi knew exactly what happened to Yuki because she was the one who accidentally killed him. And one of the rules when dealing with Renoir is you can't lie to him. Which means Nafumi lost the battle long before Higanbana got involved and Renoir knew it. Nafumi's Oh Crap! realization is priceless.