
Originally Posted by
Endless Twilight
The main attraction with the Celestial Weapons is that they ignore the target's Defence stat when used to attack physically. However, this doesn't apply to Overdrives, so in that respect they're no better than customised weapons.
There's also a variable factor for CWs. For Tidus, Wakka, Rikku and Kimahri, the CW will cause more damage when their HP is full. Yuna and Lulu work in the same way but rely on MP. Auron's damage increases when his HP is lower.
All the Dark Aeons except Dark Anima have been defeated under NSGNZ conditions (No Sphere Grid = use of the Sphere Grid is forbidden = base stats, NZ = No Zanmato = cannot use Zanmato), so defeating them by powerlevelling your characters is no great achievement. Sorry.