id say youd have better luck doing emerald first without kotr. breed some chocbo's to get kotr whilst waiting to get clouds limit then beat emerald with it and kotr if you have a gold 'bo by then. physical attacks and magic dont really do trout all to ruby. cloud normally does 9999 even when on 1 hp for me. to ruby he did about 600
i suppose you could put hades with mp absorb and keep freezing him and attack him whilst hes frozen. but that would take kinda a while. his hp is 1 million. how many 600's is that ?
you'll be needing kotr.
my suggestion is to use the oppertunity to level up mp absorb if it isnt master and get some solid chocobo breeding going.
then you can try my aforementioned strategy ^_^