Complex sentence: Fiona returns to the Academy to kill the new Supreme--however, after realizing her daughter has taken her position, Fiona renounces her self-serving, murderous intentions and dies of her cancer.
Split into simpler sentences: Fiona returns to the Academy to kill the new Supreme. However, after realizing her daughter has taken her position, Fiona renounces her self-serving, murderous intentions and dies of her cancer.