Zero, also known as the King of the Little Devils, is the regal leader of a band of minor demons known as the Little Devils that is also an unlockable playable character in the first Bayonetta.
Zero can simply be unlocked by completing the Lost Chapter, Angel Slayer. Another method exists, which consist of spending 5 million Halos after inputting a certain combinaison of inputs in front of the phones found in chapter 2. The actual inputs required are: Up, Up, Up, Up, Down, Down, Down, Down, Left, Right, Left, Right, Y.
Zero will loose all of his health aside from 1 point when he is hit meaning that he will alway die in two hits, three if all health upgrades as it push him above the damage he is supposed to take to leave him at 1 HP. His viability can be increased by various means however. He will regain health after a while in Very Easy, healing of any kind allow him to take an extra hit given how his damage is calculated, this also means that the Star of Dineta allow him to survive one more hit after he performs a complete taunt, Pulley's Butterfly also allows him to survive two more hits each time it is used.
Zero always has the ability to summon the Little Devils even without the Infernal Communicator. This gives him the advantage to have three accesories at once but the way this ability is used overlaps with Pulley's Butterfly and Sergei's Love, which lose some of their power as a result as the activation cost also goes to the Infernal Communicator. Zero is also faster than both Bayonetta and Jeanne. Due to his weird body shape compared to other playable characters, Zero has very strange animations when replacing Bayonetta in cutscenes and likewise, his weapons just float in midair when fighting.