WOW... looks like I'm playing way to slow. I'm a little later than at the middle of disk 2. Who was the tougthest boss so far?

Divinity, try to beat the game or atleast Ultimecia exactly this way. Not only without junctioning. The Ultimecia battle will be even scarier that way.

Oh... and in the Omega battle... this way the battle will actually be very hard since I your HP won't be 9999 + lack of hero Items. I guess you'll have to use GFs to block Megido Flame.