Spira is the worst to me only because the only thing people have to look forward to is Bliztball to make them happy. They're constantly under the fear that their homes will be destroyed and that they'll be killed. They can rarely live in peace for more than like two years. They're also under the false belief of a corrupt religion and even more corrupt government. FFVI and FFVII would be pretty bad too. Then again, you could say pretty much all the FF's would be bad because most of them take place in dystopian settings.