That Double Cut materia you get on Gaea's Cliff (before it, actually, in the snowfield) really helps. If you have it for 4x-Cut and Cloud with Ultima Weapon and 9999 Hp, you can attack Emerald for 40,000 damage each turn, 3 turns and it does almost the same damage as KOTR. I defeated him only because of this. By the end of the battle I couldn't summon KOTR anymore and my Limit bar was empty, so I took him down with this. Of course, this is a secondary attack, as Limit Breaks and KOTR do more damage, but if you can't use them, the 4x Cut is great.