Quote Originally Posted by Sword
What is this "Crisis Level" system? I never heard of that.
Crisis Level affects the character's limit breaks. It can be increased to the maximum by inducing the Aura status, having low HP, suffering from negative status effects (Death Sentence is the best) and having both allies KO'd.

With regards to Lionheart, the Crisis Level determines the number of hits in Renzokuken and whether or not a finishing move will be used. It does not affect which move will be used, as each has a fixed percentage:

Access to Rough Divide: Rough Divide 100%
Access to Fated Circle: Rough Divide 25%, Fated Circle 75%
Access to Blasting Zone: Rought Divie 25%, Fated Circle 25%, Blasting Zone 50%
Access to Lionheart: Rough Divide 25%, Fated Circle 25%, Blasting Zone 25%, Lionheart 25%

The Luck stat has no effect whatsoever on the choices made when using a Limit Break.

Here are the effects of having a high Crisis Level for the other characters.

Zell: More time during his Duel
Quistis: Higher damage/more statuses induced/higher success rate of causing statuses
Selphie: More powerful spells available and more castings
Irvine: More time during Shot
Rinoa: Better moves selected with Combine