Original Zero (ゼロ(オリジナル), Zero (Orijinaru)) appears as a sub-boss in The King of Fighters 2001 and is the real Zero; the Zero in The King of Fighters 2000 is his clone. He was created because the supervising designer to his character claimed to be dissatisfied with Zero's design in 2000, hinting that ideas such as his black lion pet and this newer design were designed but not used. He is recognized by developers to be the first boss to surpass Krizalid -the supervising designer's previous character- in both fighting prowess and presence.
Unlike his clone, Zero is extremely loyal to the NESTS syndicate and was disgusted to learn of his clone's attempted coup d'état. He was resting in NESTS's main headquarters during the events of 2000 and was unaware of his clone's actions until later. He was ordered by the leader of NESTS to resume their primary plan of world conquest. Since the fighting data of the world's fighters had already been gathered and saved in the main database of NESTS's computers, the cartel planned to be rid of them and take over the then helpless planet. Willing to clear his reputation of his clone's actions, Zero is commanded to destroy the winners of The King of Fighters tournament. He traps the winning team in a space ship that was disguised as a blimp. He then informs the team about their real destination to NESTS's main headquarters in outer space as well as other information concerning NESTS's intentions. He fights the Hero Team alongside, Ron, Glaugan and the revived Krizalid. When he is defeated, he urges the team to escape the collapsing ship and presumably dies honorably on board the vessel.
Zero is extremely loyal to NESTS, he would probably be disgusted if he knew of Igniz's betrayal. In spite of his loyalty, Zero is an honorable man, a good example of this is that he likes to raise children.
- The Light Arts - Unlike his clone, Zero has several powers related to Light.
- Energy Shield - Zero can create a shield of energy in front of him.
- White Hole - Unlike his clone, Zero can create a small hole that is strong enough to absorb inanimate objects.
Like his clone, he had no crouching attack animations, yet had standing attacks that must be guarded low, and could not crouch initially like typical SNK bosses. These animations and ability were gained as he was added in KOF2002UM, and is shared with his clone.
- 0 - The King of Fighters 2001
- Testament of Nests - The King of Fighters 2002 Unlimited Match
- Igniz / Zero After Versus Regular Bonus - The King of Fighters 2
- Zero Clear Bonus - The King of Fighters 2
- Toshimitsu Arai - The King of Fighters 2001~2002 UM
- Taiten Kusunoki - The King of Fighters: World, The King of Fighters: All Star
- Kaya Okuno - The King of Fighters: All Star (As Lady Zero)
- The King of Fighters 2001 - Sub-boss
- The King of Fighters 2002 Unlimited Match - Possible Boss
- The King of Fighters 2 - Boss
- The King of Fighters World
- The King of Fighters All Star (also as Lady Zero)
- One of Zero's victory poses have him doning a cape, a reference to Alucard sprite from Castlevania: Symphony of the Night, understandable as both share the dark skin, white hair and black/blue clothes.
- The bladed portion of his armor has been called a "skirt" or a "cape," but seems to resemble a Javanese male sarong, only with blades sewn into the lining.
- Zero has an alternate version in The King of Fighters All Star, called Lady Zero. A tiny version of Glaugan (Zero's black lion) appears as part of her moveset, like her original version.