It's Viola from 'The Witch's House', though honestly she feels more like the 'main character' only technically. You spend the whole game controlling her as she navigates this horrible, shifting mansion, but the whole narrative is built on a massive twist that recontextualizes everything. Saying much more gets into huge spoiler territory, but the game is famous for its 'Diary of Ellen' system where you find pages that seem to be from another girl's perspective. That's the real hook, questioning who you're even playing as and what really happened between Viola and the witch. The terror comes from feeling like you're guiding this vulnerable girl, only to have the rug pulled out from under you in the most brutal way possible. It's a masterclass in unreliable narration in horror RPG Maker games.
Trying to define the 'main character' in a traditional sense doesn't really work with this story. If you go in blind, Viola is your protagonist. By the end, your understanding of who she is, what she's done, and whose story you've actually been following gets completely shattered. The witch, Ellen, becomes just as central, but in a way you only piece together from environmental clues and those diary fragments. I love stories that make you replay them with new eyes, and 'The Witch's House' absolutely does that. The first playthrough's protagonist becomes something else entirely on the second.