I have a question for someone who has a strategy guide. I think that the way it works is this.

If you have X life, you have to be dealt X and a fraction of your life, depending on the level of the limit, to fill your limit bar.

For example, If I had Cloud with Omnislash, and 9999 HP, then I would have to deal about 18000 damage to him to get his limit break.

Does anyone know something about this?