Tales of Zestiria is a better game than people give it credit for, I know I've said it before, but the reason many people panned the story is because a lot of the themes go over people's heads.
It also subverts the culture of vengeance as a substitute for justice, and having to kill people, even those who themselves ruined lives and killed thousands, is properly presented as a heavy subject. The burden of such a decision is framed as one that couple potentially permanently stain a soul.