Ive noticed that a lot of FFs, final bosses are weak. For example: FF6, 8 and 10 are ridicoulous. Sephiroth is easy and hard at the same time, because of Supernova. Cloud was confused, and did a quadruple cut on my party = Death. Necron is hard, as his grand cross and Neutron Ring were powerful, not to mention his speed!
I reckon final bosses should be VERY powerful, but not invincible. I also think there should be secret bosses in all the FFs that are designed for the ultimate challenge. (Ruby/Emerald/Omega Weapons, Ozma, Shinryuu, Penance and FF5 Omega for instance.)
What do you think?