Brainiac (real name: Vril Dox) is an alien android appearing as a major antagonist in DC Comics. He is regularly portrayed as one of Superman's arch-nemesis (A trait he shares with Lex Luthor) due to his actions on the planet Krypton and has gone on to become one of DC's most dangerous and formidable foes since his debut.
Brainiac was created on the alien planet of Colu to act as a humanoid interface and the perfect operating system for the planet’s massive computer network. He developed by sorting and storing large amounts of the planet’s data and information and eventually gained complete sentience. Brainiac was then used as a spy by Colu’s ruling class, due to rebels springing up that were trying to bring down the oppressive government. To make him seem like a normal Coulan, Brainiac was given a "son", Quil Dox, who would later become called Brainiac 2. With his cover intact, Brainiac succeeded in infiltrating the rebels and bringing them down from within.
However he became too independent and turned on his masters, bringing them down as well. But with two groups now against him, Brainiac left Colu, eventually establishing himself on another planet called Bryak, before he was driven out of there as well. He decided to follow one of his original directives, information gathering, but now for his own gain.
Clashes with Superman
Brainiac began searching the universe for powers and techniques that would ensure his success against any opponent he came across. He eventually discovered a shrinking ray that would allow him to remove huge cities by miniaturizing them and their populaces. Brainiac began testing it on cities on planets throughout the universe, but the restoration process yielded mixed results and even utter failures.
It when the humanoid computer tried to take Metropolis that he had his first encounter with Superman. The Man of Steel managed to stop Brainiac, despite his advanced technology, and drive him away from Earth. The humanoid computer decided that Superman was the ultimate test of his abilities, one that would ensure success in his goals of conquest in the universe. Brainiac attempted many times to defeat Superman using various schemes and even joined forces with Lex Luthor due to their shared level of high-intellect.
Eventually Brainiac decided his body was insufficient to beat Superman, despite its possession of super strength and speed. He rebuilt his biological body into a more robotic one constructed out of “living metal”, thus making it so he was no longer limited to one body. This was because Brainiac could now transmit his mind into other electronic devices that could hold it or at least a large part of it. Brainiac was also able to directly transmit himself into interface with other electronic devices to control them and access other devices. He could previously do this only with specialized interface plugs, such as the one on his previous head. Brainiac used this form until Crisis on Infinite Earths, where he was destroyed, but was recreated as the biological Vril Dox.
On the plant Colu, there was a scientist named Vril Dox, who actually cloned himself to create a lab assistant, a clone that would be called Vril Dox II. After obtaining a spaceship, Vril Dox journeyed throughout the universe to obtain knowledge and captured members of numerous alien species with use of robot drones. At one point, he went to Krypton while General Zod was alive and stole the entire city of Kandor, which he shrunk and put in his ship. Vril Dox also built a remote scout unit, which he actually programmed to think it was Vril Dox.
The scout unit eventually came to Earth as a cloud of nanotech robots, taking over the body of sideshow psychic, Milton Fine, who worked under the name "Brainiac". Since he needed cranial fluid to keep Fine under his control, Vril Dox forced him to go on a killing spree. He eventually discovered that Fine did actually have psychic powers, which he used to fight Superman. Eventually Brainiac was captured by Lex Luthor, but he used his powers to take control of Lexcorp and made the company’s scientists build a version of his Coluan form.
A series of diodes on his head increased and stabilized Brainiac’s mental powers and allowed him to directly access computer banks. He continued to come into conflict with Superman, battling him with a combination of mental power and control of computers, even shrinking cities on one occasion like he did in his first incarnation. After losing access to Milton Fine’s body, Brainiac placed his mind in a new robot body called "Brainiac 2.5" and briefly sought to take Superman’s body.
Later on, Brainiac revealed he’d place a sleeper virus inside Lexcorp’s Y2K safeguards, which he intended to use to increase his powers to an extremely high level. However it instead brought Brainiac 13 from the 64th century to the present, who stole Brainiac’s form, placing his mind inside Lena Luthor, Lex Luthor’s daughter. Brainiac 13 transformed Metropolis into a futuristic version of itself, but Lex Luthor made a bargain with Brainiac 13. In exchange for control of the B13 Technology, he gave Brainiac 13 Lena Luthor and Brainiac 2.5 left with Brainiac 13.