Doctor Diehard was one of the villians native of Angor/earth-8. As all the characters from earth-8, he is a doppelganger of a marvel comics character, in his case, he is an analog of Magneto. In their last interpretation, the character included traits of Professor X.
Angor Doctors Diehard
Hans Leckter was a terrorist on the planet Angor and belonged to a group called the Extremists. He had gained his powers of magnetism after capturing an experimental nuclear weapon, that once in their possession exploded giving the group their powers. Diehard and the other Extremists, except for Dreamslayer, died on the planet Angor after the group caused a nuclear holocaust.
Doctor Diehard was recreated as a robot along with the other dead Extremists by his former teammate Dreamslayer. Once the team was recreated and functioning they attempted to take over the Earth. They were ultimately stopped by Justice League Europe . Once defeated the Extremists robots were taken to Paris to reside in Madame Clouseau's Wax Museum for display. The team including Dr. Diehard were later reactivated by Dreamslayer for a second time on the island of Kooey Kooey Kooey , and later reactivated again to be used by Twilight in a battle with Supergirl.
The character had been created on Earth-8, Hans Leckter, who had decided to form a school for young metahumans. This school was known as the Academy for Advanced Children, where children could be trained to harness, control and use of their powers. The school created a team of some of its most unique students, calling themselves the Zen Men. Even thouth the school and the team had super powers Hans Lecktor was a pacifist by nature and did not condone voilence. Hans had built a surrogate family for himself which had two children (Anna & Jack), which caused him to have little to no interest in the outside world.
Unfortunately the times of peace were limited, the Tin Man had been elected as US President, and deemed the school to powerful to exist. Tin Man gave the residents a choice: sign up and become government agents, or be outlawed and hunted down. Hans refused to compromise his pacifistic ideals and most of the school followed his lead, except the Zen Men sided with the government. The school was attacked and the people who were captured and not killed had a choice to join the Meta Militia or live in the interment camp with chip implants to prevent the captured people from using their powers.
Despite what had happened Lecktor refused to respond with violence, even when his son begged for Hans to change his mind. Only when a riot happened which ended the lives of his children Anna & Jack did Lecktor change his mind. One of his former students and leader of the Zen Men, One-Eye purposely deactivated Hans chip and urged him to act based on his beliefs. Now given this freedom Lecktor vowed to fight Tin Man's administration through whatever means possible and regardless of the cost.
Hans escaped the camps with the help of Lord Havok and relocated to West Germany, where he founded a new school for "gifted youngsters". He began training his new students hard, trying to make sure they would be better prepared and resilient to following authority blindly. Given Lord Havok's help with the escape Lecktor also became affiliated with the Extremists.
Later on a being known Monarch tried to to recruit the Extremists for his inter-dimensional army, however Monarch had destroyed the new school and killed Lecktor's wife. This caused Hans, who is using the name "Doctor Diehard", to lose self control and retaliate against Lord Havok. Lecktor tried to fight Lord Havok by gathering other Extremists on his side, but in the end was killed by his teammates.
Powers and abilities
Dr. Diehard have a vastly range of magnetic related abilities. Among them he can manipulate and channel magnetic fields, change structural metal alloys and cause them to explode and fly using magnetism.
The second Doctor Diehard is a robotic construct with the same powers, and has been deactivated and reactivated numerous times.
The post Infinite Crisis Doctor Diehard have the same abilities than the original Diehard.