I was easily able to defeat Ruby weapon at level 65 which is a far cry from the "required level off 99" most people beat him at... It is all about strategy... First I will list the required items
Items
-Sprint shoes
-Knights of the Round+Hp absorb
-Mime
-Elemental+Ultima(or comet 2 both work fine)
Thats right no ribbons, final attack, mastered materia, or anything that requires massive amount of leveling.
Now here is where the subtle difference comes that puts ruby weapon from impossibility to easy.... and i dont mean sephiroth with knights of the round easy I mean Air buster with knights of the round.....
What you do is kill off everyone but cloud and have him equipped with all the said items... 9999 hp isnt required either i went in with 8659 and never dropped below 2000+ hp with 2 characters dead ruby plants his tendrils in the ground. With his tendrils planted he does two things ruby beam and ultima. ultima is a counterattack to what i say is knights of the round but that is beacuse i didnt use any other attacks on him.
The tendrils attackwith mp sucking of status changing damage. so the first order of business cast Kotr on them. Ruby yanks them up after the casting giving you enough time to mim it w/o any damage take. because his tendrils are up the most he can do is cast comet 2 (thats where elemental comes in) physical attack and big swing. none of these can do any huge damage so mime the kotr and he will take 80-100k damage he will then throw his claws back in mime again and it will kill his claws. He will do this one final time you shouldn't even take damage for the first 3 kotr castings on ruby himself. After this ruby will begin to immediately attack with big swing physical attacks or comet 2. Comet 2 is only worriable if you don't have many stars on your elemental materia even so i took a full no miss comet 2 and came out of it with 2000 some odd damage. with Hp absorb on kotr it was no problem.