Genocide is from the 1996 Chaos! comics miniseries "Lady Death: The Crucible", and has appeared in several other Chaos! series since. He is one of the Chaos Lords (Jehovah,Lucifer , Odin, Armageddon , Brahma, Kreator, and Genocide), ancient beings who created the modern universe from primordial Chaos on accident, Genocide seesk to returen it to primordial chaos.
Genocide's early life is mostly unkown, he has stated that Lucifer is his younger brother, and it has been stated by narration taht he was perfectly content with the universe as it once was, totally chaotic with nothing defined as seperate from anything else.
At one point he married Antigone and had a two children named Vex and Scorpia, the later had a daughter of her own named Sinestra. He also became king od his own planet, Wraithworld, from which he lead a massive empire of wraiths who possessed similar nihilistic desires.
Quest to Destroy the Universe
Genocide went on a quest to find any powersource that coudl destroy the universe, and eventually found one in Odin, King of Asgard. Genocide did manage to kill Odin, but Odin was able to hide his power before Genocide could access it. Genocide attempted to conquer Asgard, but was met with heavy resistance by the Aesir and Lady Death, who raised all of the dead in Asgard in to create an army against Genocide.
Genocide found the Odin Power, and brought it back to Wraithworld, but Lady Death was able to kill him before he coudl destroy the universe (though he did manage to destroy a few stars). Later on Genocide, in typical comic book fashion, returned from the dead and again attempted to do what he before he died. he was still stopped, however.