first of all let me say this: hahahahahahaha

right down to business first of all you need final attack and Revive materia equiped then KotR and HP absorb in slot 2 and finally counter with mime (this works for 1 character and if you want more then you just master the mime and counter 2 times) you might need 1 mastered hp materia and there is an easyer way to do this but it has risk which is: HP>MP swap then quadra magic combined with KotR and mime just use it with the quadra magic and then mime to victory this is by far the easyest way to kill ruby (all you do is have the other 2 mime it and she will be dead straight away) id say good luck but you dont need it with my stratagy