Krona Programs The Manhunters To Kill Billions
The Manhunters were the first police force created by the Guardians of the Universe. When they inexplicably slaughtered all but five of the inhabitants of the planet Ryut, the Guardians decided to replace them with the Green Lantern Corps instead. Here, it’s revealed that the mad guardian Krono reprogrammed the Manhunters to carry out the genocide.
From – Green Lantern Vol. 4 #63