Marietta Edgecombe never apologized.
When she was six, she had thrown her sister across the room in a fit of anger. She couldn't control her magic then. Her mother had demanded that Marietta apologize, bust she didn't. Laura had broken her dolly and had deserved what she got. Even if it was an accident.
When she was ten, her best friend Sara had gotten a new dress. Marietta loved that dress; it was pink and had frills all along the edges. She had begged and begged her parents to get her that dress, but they had refused. The next time Sara had worn it; Marietta hadn't been able to stop herself from pushing Sara into the mud. She hadn't apologized then because Sara had something that she didn't, and she was justified.
When she was fourteen, Cho started going with Robbie Hartman. Marietta had liked Robbie since first year, but Cho had gotten him, because Cho always got the guy. But Cho was a prude, and Marietta was no such thing. So eventually, Robbie stopped liking Cho and liked Marietta instead. Marietta had felt a little guilty when she looked into the sad, confused eyes of her friend, but then Robbie would put his hands on her hips and she never apologized because finally someone wanted her.
When she was sixteen, she told Umbridge about the DA. It was easy; she had no obligation to help rule breakers, even if Cho was going out with the worst one. There had been an unintended backlash however. Her face was scared-the word SNEAK blatantly tattooed across her face. No one wanted to talk to her after the incident, even those that hadn't been in the DA. Everyone except Cho. Cho stood by her through the entire ordeal, even though it meant losing her boyfriend and the respect of many of her peers. Her friend never complained and hardly left her side, lest Marietta be subjected to even a hint of a sneer in her absence. After Marietta told Umbridge, they were both isolated. It was all Marietta's fault. She knew it. But she never apologized.
When Voldemort came back, she wanted to help. But she was graduated by then. No one that she had been in school with- Fred and George Weasely, Katie Bell, Oliver Wood- none of them trusted her. But she still had her DA galleon. So when she felt it burn on the 2nd of May, Marietta Edgecombe went to her old school. She fought and cried alongside everyone else. Alongside them, but not part of them.
A giant kicked down part of the castles outer wall during the battle. Marietta was crushed under the debris before she could lift her wand to stop it. Just before Marietta died, she worried that those that found her would think that she was on the other side. Because she was a SNEAK. But she hoped, as her heart pumped for the final time, that they would know that for once, she was sorry.