Oh, I forgot to add a very good boss design.
The Cloud of Darkness DS-form plainly rocks.
Very good 3D + Very nice animations + Nice Surge Cannon, yeah, an excellent looking Final Boss.

Only BAD thing about that bossy is a) Her music, not really epic and b) Her death-animation. She dies like a NORMAL boss?! WTF? It's the Final Boss! Even in the original NES-verison they had her sink away! And in DS she doesn't! There's even a victory fanfare! In which Final Fantasy had Final Bosses a plain normal, boring death animation and a victory fanfare?! They made everythign so close to the original and now this?!

Besides those freaking bad points, good looking boss. This topic is about their design, anyway.