Bruno Mannheim was an organized crime boss from Metropolis.
Bruno Mannheim was the leader of the criminal organization known as Intergang. This position left him with vast resources, which he would use to control the underworld. He was also amoral and had no compunction using innocent people for his own means. In one incident, Mannheim went to a toymaker, Winslow Schott Sr. and offered to finance the building of a toy factory. However, this financing came at a price: the toy factory was to be used as a front for a numbers racket. When the police discovered this, Mannheim was only named a suspect while Schott was taken to jail where he later died. As a result of the toymaker's death, his son was shuttled around to various homes and became twisted as a result. The toymaker's son would return years later as Toyman to torment Bruno.
Years later, Mannheim founded a park in Metropolis in his honor. This park was a public relations move to improve his public image. However, during a rehearsal of the opening ceremonies, a squadron of toy planes armed with machine guns started shooting at him. Mannheim suddenly found himself being confronted by Toyman, who turned out to be Schott's son. Mannheim was kidnapped and taken off to Toyman's lair where he was nearly executed. However, Lois Lane managed to prevent the execution and after Toyman tried to kill her, Superman arrived. After Superman destroyed most of Toyman's toys, he dropped several bombs into the lair but Superman rescued both Mannheim and Lois. Mannheim had not heard from the Toyman since.
In spite of his rescue and near death experience, Mannheim learned nothing and tried to rob the Metropolis Gold Exchange using a military grade tank. When his plans were subsequently foiled by Superman and his weaponry rendered useless, Mannheim threw a fit until he was visited by Kanto, an agent of Darkseid. Kanto supplied Mannheim with advanced technology so that he could defeat Superman. Using this new technology, Mannheim succeeded in incapitating Superman and was about to defeat him with a gun capable of firing a concentrated energy beam, but was thwarted by Dan Turpin. Mannheim managed to escape and followed Kanto to Apokolips. Upon arriving, Mannheim met his new ruler: Darkseid.
Mannheim stayed on Apokolips for an unspecified amount of time where he learned more about the technology of Apokolips and began to believe that with his newfound knowledge, he could defeat Superman. However, Darkseid refused to return him to Earth claiming that he would not tolerate someone failing him twice. Mannheim was still under Darkseid's favor until he questioned how Darkseid could take Kalibak seriously. Angered by the fact that Mannheim questioned his judgment, Darkseid sent him to the slave pits of Apokolips.
When Darkseid planned his first invasion to Earth, Mannheim was returned to Metropolis so that he could assist in the invasion. Given Apokoliptian tanks and the promise of becoming a king, he first stole a large amount of money from the SCU but this was unfavored by Darkseid who did not want him wasting the technology on petty theft. Now taking his orders more seriously, Mannheim began to attack military bases to weaken Earth's defenses. However, after the arrival of Orion, he failed.
Darkseid was unconcerned, however, and sent Mannheim to finish his final task: to sabotage a nuclear reactor so that it would melt into Earth's core and turn Earth into a second Apokolips. However, once it was done, Darkseid betrayed Mannheim and left him for dead, keeping his earlier promise about crowning him a king, but a "King of Fools". Mannheim tried to escape in a motorboat, but was too late. When the reactor detonated, Mannheim's boat was caught in the explosion and he was killed.