DRK skill: Living Dead

[Flay_wind]

There are no DRKs in the series after this until FFXI. In FFXI DRK is unlocked by slaying 100 enemies with the Chaosbringer great sword. The Job's 2hr ability is Blood Weapon, an ability that makes all hits drain HP for 100% of the damage dealt. The job goes on to acquire the Drain and Aspir spell line as well as attribute absorption spell lines. Drain spells and hits within FF lore started in FFII, and were unique to undead monsters and the Blood Sword. Furthermore, within FFXI, DRK gains Arcana Killer as a trait, which is a trait intrinsic to Undead in the game as Undead <-> Arcana, both intimidate the other.

Surprise! FF X-2 had a Dark Knight class Dress Shere which was likely an inspiration for FF XI and XIV DRK.
It used a great sword as a weapon and it was a tanky class (iirc it had the highest health and defensive growths in the game, but was somewhat slow) with emphasis on status effects, both status immunities and status inflicting spells like Confuse, Bio, Break and Doom under Arcana ability. They also had Drain spell and a Darkness skill which sacrificed some hp for a powerful non-elemental attack to all enemies. Also they had Charon aka Self Destruct.