This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / The School for Good and Evil
Despite everything that had been said and done, despite all that had passed between them, when it looked like an army of enraged Evers was coming to kill Sophie, Agatha, embracing her, says, "I won't let them hurt you."
Made even more tragic when Sophie replies, "I wish I could say the same."
All of the wolves and fairies were failed Evers and Nevers respectively. And a lot of the kids taken from Gavaldon for the School of Evil weren't necessarily evil, but just rowdy kids, and they wound up having to become the villains of the fairytales we were raised on.
Sophie at her mother's grave with Agatha, telling her about her family.
EVERYTHING about the ending of A World without Princes. Agatha and Tedros have confessed their love for each other, but Sophie, in her desperation for True Love, willing accepts to be with the resurrected Evil Schoolmaster, thereby breaking the curse that kept Good and Evil in balance. Now both schools are dark, scary and EVIL, the armies of boys and girls are ready to slaughter each other, and Sophie and Agatha, once true friends, are separated. All because of a misunderstanding and a lack of trust.
Made worse by the fact that Sophie, ofallpeople, asked the correct question a few pages back: Why canít the princess (Agatha) have the love of her prince and her best friend at the same time?
The Last Ever After really expands upon Cinderella's story. For starters, when her father passed away, her evil stepmother initially wanted to sell her to Bluebeard as a wife. At the time, Bluebeard was already known for chopping up his wives. This was also before Cinderella attended the school, meaning that she was just a child. Her sisters, who genuinely cared for Cinderella, suggested that she act as their maid instead, saving her life. The sisters were raised believing that they were destined to attend the School for Good and win themselves a pair of princes. Cinderella was satisfied with hearing about their fantasies and spending time with them when her stepmother wasn't around. When she was picked to attend the school Cinderella was devastated, and blamed herself for having taken an opportunity she felt should have gone to her sisters. She was terribly homesick, and ran right back home after graduation. Her sisters were very bitter upon her arrival, but eventually warmed up to her again. When the ball came along, Cinderella became excited and happy for her sisters to get their chance at a prince, so much so that she desperately wanted to join them. That's when Professor Dovey appeared and granted her wish. Cinderella didn't want a chance with Prince Charming; she wanted to be with her beloved sisters! However, the prince chose her, and this enraged her sisters. Cinderella wanted the prince to be with one of them, and ran back home to prove it, but her prince found her again. When the glass slipper fit, Cinderella insisted that she'd only go to the castle if her sisters could come with her. The prince, remembering how they'd behaved at the ball, refused and told Cinderella to choose, but secretly waited outside of the house. Sure enough, Cinderella's stepmother tried to kill her, so the prince was forced to kill her in order to save her princess. Cinderella's stepsisters awoke the next day she was gone and their mother was dead. They wanted revenge and continued to plot against Cinderella, so her prince had them killed behind her back.
In climax of The Last Ever After, when Agatha's words finally get through to Sophie, and she destroys her ring thereby killing the Schoolmaster for good. It's all cause for celebration at first, but because this is The End for Sophie and Agatha's story, they are officially fairy tale characters, so the girls cannot exist in the Reader World. As they fade away from Gavaldon back to the Woods, they bid goodbye to Stefan forever, whom Agatha has only recently learned is the father she always wondered about.