chaos: I have to agree with Ultima on every single aspect, as always when it comes to this subject!

Rubedo: Ruby and Emerald both had strategies to make them very vulnerable. For Ruby, have KOTR and have the "absorb" Materia attached to them, so when you attack, and Ruby counters with Ultima, you still live (Or at least something to that extent)

Trowa: Through my first play, when I didn't level up all the way, I found Omega harder, simply because of Terra Break and some of his other killer moves. Afterwards, also after a ton of junctioning, and mass leveling up at the Island Closest to Hell, Ultima turned into a pain in the ass. *Sits and stares and sits and stares*