[Yggdrasill]

There is a really easy way to beat the weapons and only Cloud is needed, you'll need:

Materia needed:
5 "Mime" materia's.
5 "Counter" materia's.
Underwater materia

You'll also need the Omnislash Limit-break.
To beat Emerald easy just put the Mime and Counter in linked slots like this Mime=Counter.
Once you begin the battle have your limit-break already filled and have Cloud use Omnislash, now as soon as Emerald attack's you, you'll use Omnislash 5 times in succession. It's a pretty easy and sneaky way to beat Emerald and Ruby, the same thing works if you use 'Knights of the round' instead of Omnislash.