The original Bizarro was the result of Luthor grafting Superman's DNA into the body of a young boy named Bobby. However, the cells took over Bobby, turning him into a bizarre monster. Going on a rampage, Bobby was destroyed by Luthor. Bobby's new cells were then used in the creation of the second Bizarro.
The second Bizarro was started as Project B-0. Activated before his time, B-0 was incomplete and had become yet another Bizarro. Used to fight against the Crime Syndicate, B-0 remained completely loyal to Luthor. B-0 Eventually dubbed himself Bizarro and continued to aid Luthor throughout the ARGUS Insurgency. By the end of the Insurgency, B-0 was killed by Mazahs.
On Earth 2, Bizarro existed as an almost perfect clone of Superman mindwiped to loyally serve Darkseid under Steppenwolf as Brutaal. After realizing that Steppenwolf cared only for himself, Brutaal killed the New God and took up Darkseid's cause for himself. Getting Mr. Terrific and Terry Sloane to start working on an amplified Boom Tube device to subjugate Earth 2 to Apokolips, Brutaal's multiversal servant, Kaizen Gamorra, tried to bring Prime Earth under the hands of his master. Brutaal then learned that the conscience of his deceased wife, Lois, had been transferred into the Red Tornado robot and revealed he was doing everything willfully and wanted to serve Darkseid. To prove this, Brutaal murdered his own adoptive father. Upon discovering that Alan Scott was opposing his plans, Brutaal headed out to try and stop him, only to be confronted by Val Zod. In his battle against Val Zod, Brutaal was defeated and proceeded to disintegrate into dust, solidifying his status as a mere clone.
Earth 29, also known as Bizarroworld, was a world simply inhabited by "Bizarro" versions of the heroes of Earth 0. The Bizarro version of Superman was simply known as Bizarro. When Superman fell through the cracks of reality from Earth 0 to Bizarroworld, he fought Bizarro before working with him to fight Bizarroworld's Doomsday.