Each of the characters are able to learn one unique ability in one of their Crystariums that none of the other characters will be able to access. Several characters have access to a unique ability that, while named something, operates the same as some of the other unique abilities.
These unique abilities ignore an enemy’s resistances entirely. This means if they are resistant to any type of magic or attack and it also means that any debuffs applied to the enemy will not increase the amount of damage dealt.
What the unique ability does is dictated by which Crystarium the ability can be found in and unlocked in.
Sovereign First (Snow)
Highwind (Fang)These abilities are intended to deal heavy amounts of damage on their own. After the move has completed, the enemy’s Chain Gauge will reset to 100% which means that these attacks should only be used just before a Stagger is about to expire in order to inflict maximum damage without disabling the Stagger too quickly.
Army of One (Lightning)Cold Blood (Sazh)
Last Resort (Hope)These abilities will provide a significant boost towards the enemy’s Chain Gauge. They can be used to greatly increase the percentage of the Chain Gauge or towards Staggering an enemy and it isn’t intended to deal as much damage on its own. The best tactic is to have these abilities trigger a Stagger before swapping over to a paradigm that includes 
Commandos.
Death (Vanille)Vanille’s Death spell is one of the most useful abilities in the game. When it’s cast it has a 1% chance to inflict an instant kill on the target. This can be increased by casting 
Imperil on the target beforehand, bumping the 1% chance up to 4%.
