Well, that is your opinion... I just see both sisters suffering in their own ways. Anna thought for 13 years that her sister hated her for the reasons she didn't knew and she never learned proper social skills. But Elsa was never allowed to grew up to an adult and she lived her life in a constant fear that she might hurt or kill people, never being able to learn controlling her powers or emotions. Both of these scenarios are so heartbreaking that I have to lie on my back for a while and stare at the ceiling. They are both victims in their own way, and that's why I'm giving love for them both, being unable to choose which one of the sisters is actually my favorite.
True, to each their own. They've both had their challenges to overcome.