Alicia from Level 99 Villainess is a tragic figure, at least in the novel versions.
She is supposed to be the protagonist, the wielder of light magic who will defeat the Demon Lord and save the country. She starts off weak, but she should grow over the course of the story, both in terms of power and emotionally to face the challenge at the end.
This is all thrown off by Yumiella appearing at the start of her story.
Yumiella is potentially the most powerful person in the world, and could probably solo the Demon Lord from the beginning. She also looks like a cloud of darkness with glowing eyes to Alicia.
Yumiella also shows up Alicia's harem, giving them inferiority complexes that keep them emotionally stunted and cause them to over-focus on protecting Alicia, which stunts her magical and emotional growth. She doesn't need to learn to stand for herself if she has three strong guys doing it for her. And they don't need to confront their feelings of inferiority if they have sweet, weak Alicia to protect and make them feel strong. Meanwhile Yumiella is still stronger than all of them, a steady reminder of all their inadequacies.
Yumiella tries to help, but her own lack of social skills and empathy lead her to traumatizing Alicia further in her attempt to level grind her. Now Yumiella doesn't only look monstrous, she has also forced Alicia into a dangerous situation and would not let her leave.
So when it's time for the final battle, time to fight the demon lord, Alicia finally takes some agency and attempts to slay the demon who has been tormenting her.
I've been thinking lately about how to make a character who lacks agency interesting, and I think it's by giving a lot of impact to the choices they do make.
