Chronos is a fictional character in the DC Universe and an enemy of the Justice League.
A petty criminal all his life, David Clinton realized he was being arrested because he didn't take the time to plan his crimes properly. Admiring the clockwork precision with which everything in prison was run, he decided he would make time work for him rather than against him. Fascinated with timepieces and deft with his hands, and possessing an inventive mind, he spent the remainder of his prison sentence laboring in the prison workshop, learning all he could about clocks and their mechanisms. Finally released, Clinton designed a costume and embarked on a new criminal career as the time thief called Chronos. His crimes brought him into repeated conflicts with Ray Palmer, the super-hero known as the Atom.
Justice League Unlimited
David Clinton had been mocked by his time traveling theories, his peers spurned him for his claims of discovering time travel, lost both his tenure and reputation. However, Clinton came through as he developed time traveling technology and incorporated it into a 'Chronosuit'. He used the device to collect rare relics from the past. However, he initially only took stuff that wouldn't be missed, lest he change the timestream. After having enough from his verbally abusive wife, Enid, Clinton went nearly 50 years into the past and attempted to steal Batman's utility belt from the Justice League's Watchtower, but he was thwarted by John Stewart, Wonder Woman, and Batman. He jumped into a time vortex, but the League members chased him.
Clinton arrived in the Old West (1879), where he was jumped by a group of men working for the local crime lord, Tobias Manning. They stole his time traveling device, which Manning used to steal advanced weaponry from the future, and then take over the town of Elkhorn. Clinton was kept behind bars for nearly six months ― until the League finally caught up with him ― to teach Manning how to use the technology he couldn't understand. When the Leaguers, Bat Lash, El Diablo, Jonah Hex, and Ohiyesa Smith defeated Manning and his outlaws, Clinton managed to retrieve his belt and fled in a time portal, followed by Stewart, Wonder Woman, and Batman again.
Clinton's newfound power drove him insane, and he became a megalomaniacal sociopath. He now traveled back to his own time and asserted himself as "Lord Chronos", the undisputed master of space and time. He no longer cared about time paradoxes, and started collecting all sorts of relics from the past while poaching for advanced technology from the far distant future. He took over Gotham and used the city as a big storage space to collect his memorabilia. He also made himself king, escorted by a very much tamed Enid, now scared of Chronos's temper and mood swings, as well as put his mother in-law in an undisclosed "thing". He endowed The Jokerz Bonk, Chucko, Woof, Ghoul and Dee Dee with special enhancements and enlisted the clowns as "security". He also had a new, upgraded Chronos-suit.
Having knowledge of the future and the past, he sent his Jokerz to intercept Batman, Stewart, and Wonder Woman, who had come after him through the time vortex. However, the Jokerz failed because the JLU had been tipped off, and Batman, Static, and Warhawk aided the Leaguers in their escape. Chronos ruthlessly disposed of the traitor ― Chucko ― by leaving him in the past, seconds before the dinosaurs were made extinct by a meteorite. Due to Chronos's tampering with the past, the timeline started to unravel, so the League and the JLU tracked him down to reprogram his belt and restore time. Chronos fled to the Beginning of Time, to reset it and make himself a god. However, he was promptly intercepted by John Stewart and Batman, who reprogrammed the time-belt. This reversed Chronos's doings, trapping him in a time loop, right before everything started: his wife underminding him.
Batman: the Brave and the Bold
Chronos is a time-controlling villain and an enemy of Atom (Ray Palmer). When Ray Palmer retired from being Atom, Chronos wasn't seen for awhile. Some years later as seen in "Sword of the Atom," Chronos resurfaces causing Ryan Choi and Aquaman to look for Ray Palmer. By the end of the episode, Ryan Choi returned to being Atom and helped Batman and Aquaman defeat Chronos. He later returned in "Triumvirate or Terror" as a member of the Legion of Doom.
Chronos debuted in Atom #3 (October-November, 1962), and was a creation of Gardner Fox, Gil Kane and Murphy Anderson. David Clinton was petty crook who believed his failures were a consequence of his bad timing. While serving sentence in prison, Clinton studied and trained himself to synchronize his actions with clockwork precision. When he got out of prison, he donned a flamboyant costume and dubbed himself Chronos, the Time Thief. He also developed various time related gimmicks (sundial-shaped hovering platform, razor-sharp hands, and explosive hourglasses) to meet his goals. Chronos pitted himself against the Atom (Ray Palmer), who thwarted him on every occasion. Eventually Chronos developed devices that could actually influence the local flow of time and tamper with time, such as a time machine. Chronos soon began using his time traveling abilities to become rich, but he was eventually sent to prison. He later sold his soul to Neron, who bestowed upon him the inherent ability of time traveling. Chronos ended up losing touch with timeline and dwindled into oblivion.
Whilst not considered canon to the main DCAU, a version of Chronos more similar to his mainstream comic book version was seen in the Justice League Adventures series. At first portrayed as a villain, he was soon seen in a more benevolent light as he tried to prevent an event which took the life of his brother, Robert 'Bobby' Clinton. However, he was helped by a future incarnation of himself, from the JLU/Batman Beyond era, who urged him to try and try again after continually failing to save Bobby. This began to cause significant damage to the timestream. Eventually, he was stopped by The Flash and The Atom after they brought Bobby to his present time and he convinced David to let go of the past and move on. With that, his older incarnation was erased from history and he turned himself in. Later, whilst in prison, the League brought a young woman to visit him, who was revealed to be his future daughter from a repaired timeline named Bobbi Clinton, in honor of his deceased brother. This presumably gave him the hope to give up the title of Chronos and live a normal happy life.