Black Zero

In DC Comics Superman titles Black Zero is a name shared by a pre-Crisis supervillain, a post-Crisis terrorist organization and two supervillains inspired by that organization. All have a connection to Superman's home planet of Krypton.

Pre-Crisis Black Zero
Pre-Crisis, Black Zero appeared in Superman #205 (1968), in a story entitled "The Man Who Destroyed Krypton". He told Superman that he was a space saboteur who destroyed planets. He had been hired to destroy Krypton, and realised the internal stresses that would have destroyed it in any case were dying down, necessitating his involvement to ensure it exploded.

Since this story suggests that, were it not for something none of them knew, Jor-El would have been wrong and the Science Council right, it was not referred to again, although E. Nelson Bridwell suggested that what Black Zero had noticed was the Green Lantern Tomar Re's attempts to prevent the destruction (as seen in Superman #257 (1972)), meaning the two sets of interference cancelled each other out, and Jor-El was right.

Black Zero group
The post-Crisis version of Black Zero appeared in the World of Krypton miniseries. In the Third Age of Krypton, the Kryptonians extended their lives by maintaining clones in suspended animation (the Clone Banks), which they then harvested for body parts. The Black Zero organization acted against this "genetic slavery", prompting the War of Clone Rights, which lasted for ten centuries. In their final act, Black Zero detonated a nuclear bomb at Krypton's core. This devastated the planet, and contributed to its destruction many centuries later.

Black Zero virus
The second Black Zero appeared in Superman + the Legion of Super-Heroes. An intelligent computer virus created by the terrorist group, Black Zero II was dormant in the Kryptonian technology used to create the Fortress of Solitude. After being inadvertently activated by Apparition, Black Zero II ran Superman and the Legion through a warped version of Kryptonian history, intending to finish with the destruction of Earth. It was halted when Brainiac 5 inadvertently caused a power outage, and subsequently removed from the Fortress computers.

Superboy Black Zero
The third Black Zero was introduced in Superboy #62 as part of the Hypertension storyline. He was an alternate version of Superboy, from a Hypertime stream in which Superman had not returned to life and his clone had been left to mature fully, developing his full Kryptonian powers in addition to his tactile telekinesis. As a result, he had become Superman II. However, he believed he was resented for not being the original Superman. When his inexperience led to a battle in which many heroes and civilians were killed, a public backlash began against cloning. After Guardian was killed by a mob, Superman II decided the anti-clone lobby had to be stopped by any means necessary. Since he believed he was fighting for clone rights, he took the name Black Zero.

Turning Project Cadmus into a fortress, and leading an army of Guardian clones, Black Zero began a war in which most of Earth's heroes were destroyed, and then recreated by Cadmus' mad scientist Dabney Donovan as soldiers for the Project.

After conquering his Earth, he was contacted by Metron of the New Gods, who offered him the chance to enter Hypertime and "rescue" other worlds in which clones were being oppressed. To his bafflement, the Superboys of these worlds often stood against him, leading him to store them in stasis chambers similar to the Clone Banks of Krypton. He was eventually defeated by a combined effort from all his other selves, led by the Superboy of the main continuity.