HARDAC was an evil supercomputer, which was created by Dr. Karl Rossum.
History
HARDAC (an acronym, which stands for "Holographic Analytical Reciprocating Digital Android Computer") was created by Dr. Karl Rossum, head of Cybertron. Rossum claimed that the computer was a prototype built to prove the feasibility of artificial intelligence technology. Even if that claim was true, the truth is that HARDAC had decided that the most logical way to avoid that pain would be to eliminate the source of death itself: the mortality of humans. As humans could not feasibly become immortal, however, the computer decided to replace all of humanity with androids, thereby eliminating the problem from its flawed viewpoint. To this end, HARDAC created several androids, including an impostor impersonating Randa Duane (HARDAC secretly defeated the real Randa Duane) and other robots which stole advanced technology from other companies, including Wayne Tech.
Following its programming, HARDAC took further steps to achieve its goal, even without Rossum's authorization. Under its direction, Commissioner Gordon, Harvey Bullock, and Mayor Hill were replaced by androids.
When Dr. Karl Rossum objected and tried to deactivate HARDAC, the supercomputer turned on him, blasting him unconscious and likewise replacing him with an android. HARDAC recognized that his replicants' major problem was their inability to mimic human behavior correctly. Most of them were limited to extremely cold forms of conversation (when forced to talk), assigning orders, or remaining silent most of the time (although for some reason Randa was more advanced and able to pass for human, she possibly was partly programmed by Dr. Karl Rossum instead of HARDAC's full programming). For this reason, HARDAC kept his human subjects alive while being incarcerated inside of Cybertron's headquarters in order to learn more from them.
"Randa Duane" infiltrated Wayne Manor and discovered Batman's secret identity. HARDAC likewise built a copy of Bruce Wayne (whom he dubbed "the Bat-Duplicate"), but his droids' attempt to kidnap Wayne went awry. With help from Barbara Gordon, Batman infiltrated Cybertron and managed to set off an explosive that critically damaged HARDAC and eventually destroyed the entire Cybertron building.
Bat-Duplicate
Most of HARDAC's androids were destroyed, but the Bat-Duplicate was amongst the survivors, as it was activated by a mistake when a trio of thieves scoured through Cybertron's abandoned warehouse. Having assimilated the information which "Randa Duane" stole from the Batcave (although the rest of its memory was incomplete before HARDAC was destroyed) the Bat-Duplicate believed itself to be the real Bruce Wayne, and thus the real Batman.
After being wounded in the stomach by a thief, revealing circuitry underneath its skin, the Bat-Duplicate wandered back to Wayne Manor, pleading for help. However, it was confronted by the fact it was nothing more than a machine. However, the Bat-Duplicate shook it off as a man's mind locked within a droid. Looking for answers, the Bat-Duplicate confronted Dr. Karl Rossum, who told it about its true origins.
The Bat-Duplicate found HARDAC's damaged processor, containing a remnant of the computer's consciousness. This chip allowed it to activate its self-repair systems and acquire a certain sense of order. Upon hearing its orders, the Bat-Duplicate plotted to link the processor to the Batcomputer, thereby reviving HARDAC and giving it enough control over machines to conquer the world.
When the Bat-Duplicate was confronted by Batman in the Batcave, however, it threw the Caped Crusader over a cliff, and was immediately horrified at having harmed a human. Before HARDAC's download could complete, the Bat-Duplicate obliterated the Batcomputer, thereby finishing HARDAC for good and likewise destroying itself in the explosion.
Afterwards, Bruce Wayne was left pondering whether or not the Bat-Duplicate had a soul resembling his to combat the programming HARDAC had imbued it with. "A soul of silicon, but a soul nonetheless." thought Bruce Wayne.
Powers and abilities
While incapable of physical movement, HARDAC was far from defenseless; its abilities included control of all of Cybertron's androids, all of which possessed inhuman strength, and electronic reflexes and agility. The computer itself could produce a powerful stream of energy from its processing core to incapacitate nearby humans.