I used Cyan, Locke, and Gau for this. Yeah, Number 128's a bitch, You just gotta keep hitting hard and doing lots of damage. With Sabin in your party it shouldn't be to hard. Just have him pump out lots of Blitz's. Just have Cyan use Swd Tech 1 and hopefully Locke's equipped with a Half Moon which can do a hefty amount of damage. Use an esper every now and then too.