Beginnings.

His first appearance was in Justice League of America number 12, during the Silver Age, he was a criminal physicist named Dr. Arthur Light. In Secret Origins #37 it showed that he was actually the second Dr. Light. The first Dr. Light was his partner at STAR Labs, a scientist named Jacob Finlay. Finlay had used a technically advanced suit to control light as a small-time superhero, but was accidentally killed by Arthur Light while his career was still taking off. Arthur took the suit and the "Doctor Light" name and used them for criminal means. He was then haunted by Finlay's ghost throughout the years, but usually used the light generated by the suit to drive off Finlay's spirit.

Doctor Arthur Light was quite a small villain of a large number of heroes. He was mostly a villain nobody would care much about and was considered a small threat. He first fought the Justice League and when he lost badly to them, he decided to fight their sidekicks, the Teen Titans. He then organized a small group of super villains who he named the Fearsome Five, but after being defeated by the Teen Titans, Light was expelled from the team quite violently. Each criminal caper led to Light's defeat, often humiliating him in the process. Light's most humiliating and scarring defeat was by Little Boy Blue and his Blue Boys, who were a group of children without any superpowers.

Volunteer for the Suicide Squad and Death.

Because of his self-doubt and guilt, which was forced on him even harder because of Finlay's ghost, he volunteered for the Suicide Squad, a group of incarcerated super villains who performed dangerous missions for the US government in exchange for clemency. On a mission against the patriotism-themed super-team called the "Force of July", during their battle, he managed to kill the youngest member of the crew, Sparkler, who was just a mere child.

After the shock of becoming a murderer, Arthur was convinced by Finlay's ghost to take a turn in the other direction, and try a hero's path. This did not turn out well at all, as he was murdered by the Parademons on Apokolips. Light was thus sent to Hell, for his corrupted deeds and murder of a child, where he was physically reunited with Finlay. Both men were released from Hell and returned to life, but it seemed to be a prank by the demons of hell, because when they returned they soon died again: Arthur Light suffocated because he was still inside his grave when he came back to life. The rotting corpse, which was Finlay clawed his way out of his grave, only to be killed by a family of religious vigilantes. Arthur Light was then again granted a return to life, but when he did, he was high in the air. He barely survived the fall, which was most likely intended to be fatal.

Dr. Light, now free from Finlay's hauntings, attempted to rejoin the Suicide Squad, but his appeal was summarily rejected by Amanda Waller. He was briefly trapped in the Green Lantern's power battery, and because of that he was transformed into living light for a short amount of time. He later joined a short-lived incarnation of the Injustice Gang, in which he assisted Lex Luthor in building holographic duplicates of the JLA.

Identity Crisis.

In a 2004 series called - Identity Crisis, revealed that Arthur Light had raped Sue Dibny, the wife of Elongated Man, some time in the past. Later in the DCU it shows that Dr. Light is a serial rapist and Sue Dibny was not the first woman he raped. The Justice League decided to wipe Dr. Light's mind by asking Zatanna to use her magic, so that their loved ones would be protected. Zatanna accidentally gave him partial lobotomy, while explains how he went from a foe of Justice League to being a low class villain of the Teen Titans. Despite that, Dr. Light managed to recover his memories sometime later and swore revenge on the Justice League.

Dr. Light's Revenge.

While he did manage to actually extract his revenge on the Justice League, he did manage to put up a fierce battle with the Teen Titans, that he actually almost won.

First, he kidnapped Green Arrow and used him as bait to start his revenge on the Teen Titans. When the Titans responded to the call and came, Dr. Light attacked without any remorse. He did not hold back anything and almost managed to kill the Titans. The Titans called in every hero who had even been a Titan in for help before Dr. Light could deal out his final blow. When all of them had arrived, Dr. Light was finally defeated, however with major effort and very barely. Batman and Batgirl appeared to take him to prison, but in truth appeared to be Deathstroke and Ravager, who offered him a place in the new Secret Society of Super Villains, a large villainous organization headed by Lex Luthor. Dr. Light, hungry for vengeance and power accepted without a second thought.

When he became a Society member, he was able to help Merlyn and Deathstroke defeat Green Arrow in Star City. Dr. Light then attacked and absorbed a great deal of the other Doctor Light's power, later revealing that this "treatment" was another one of his rape victims. He hired Killer Frost and Mirror Master to distract Green Arrow and Black Lightning while he attacked Green Arrow's family, Speedy and his son Connor Hawke, killing a large number of students at Mia's high school in the process. When Black Lightning and Green Arrow caught up to Dr. Light, he trapped Black Lightning, Speedy and Conner inside their new apartment building after Deathstroke blew up the last one. Dr Light then led Green Arrow on a chase through Star City until they both ended up in the park and Green Arrow faced off against Merlyn in a duel with bows and arrows.

Powers.

Dr. Light has the ability to manipulate light for many purposes, using his suit. Later, he managed to acquire these powers and use them without having the suit on. He can manipulate light around himself to become invisible, create solid blasts of energy, make force fields and constructs, cast illusions and fly. By repulsing photons only using his mind, Dr. Light can make areas of total pitch-black darkness. He can power himself up by absorbing light from the surrounding area, but his limit is not known. He can basically take control of anything that shines light, even dimly. This included Green Lantern's ring, Superman's laser eyes, magic lightning from Wonder Girl's lasso, etc. This control extends so far that he can draw out energy even if it is not being used. For example, he could see Superboy's heat vision in his body even when it wasn't being used, and was able to pull it out of his eyes against his will and use it as a weapon. He also showed a feat where he would take away "internal light" from other super powered people, such as the Ray and the female Doctor Light.

Dr. Light also has a genius level intellect, he is a genius in the field of physics. Although his mind wipe cause his intelligence level to severely drop, it has eventually returned to its previous genius level intellect.