I beat him at level 75. Cloud had the final attack/Phoenix combo (which I didn't even need), and Yuffie had conformer and 4x attack. One or two mastered hp up materia, some megalixers, and I was set. I didn't even have knights of the round!
The trick is that aire tam storm does 1111 damage for each materia you have, so if you only have two or three, you're okay!
Ruby I had KOTR and Mime. I inputted the commands, ate dinner, and saw that I had won.