Zero/Xero

"'Your way over you head kid..but ya got guts I will give you that.' Zero to Kazui "Zero/Xero (ゼロ/ゼロ, Zero/ zero) Also known as Alpha. Is the ruler of the 6th layer of hell, and one of the lord of darkness. Zero is a wolf-human demon hybrid, and the sixth strongest next to Virus, Lucifer, Ragnarok, Lurker, and Crocodile. Despite supposedly being weaker, his abilities are devastating and equally as destructive. He can unlock a special form which makes him virtually stronger than anybody.

Zero is also unique as he actually shows compassion and semi-sympathy for opponents he doesn't fight women unless he has to. He saved Kazui from a Doll soldier. Protected him from the others especially Crocodile's hunger. He shares a symbiotic relation with demon wolf named Xero who acts as a weapon and a vassal for his potential power.

Personality
Zero is a honorable and empathetic warrior of hell. He understands Ichigo's reason for invading hell, but he still feels a need to cleanse the world of Ichigo's inner hollow. He is loyal and always keeps a promise. He is also more calmer and more relaxed during battle.

He and Xero have a good relationship, and work together as a team. Zero also has a code of honor which annoys his fellow lords of darkness especially Lurker, Lucifer, and Crocodile.