Two-Face

Harvey Dent was the District Attorney of Gotham City, and a close, personal ally of Batman. Unfortunately, the notorious gangster, "Boss" Maroni, threw acid in Dent's face, severely disfiguring it on the left side, leaving the right side unharmed. Because of his new appearance, Dent underwent a mental breakdown and became the insane crime boss Two-Face.

Early Life
Harvey Dent was born into a life of hardship. Growing up in a lower-class family, Dent was raised with an instinctive dislike and mistrust for the upper-class. His father was a politician, an evil man, Dent's father would gamble, get drunk, and abuse his son constantly, sometimes deciding whether he would beat him or not on the flip of a coin. Some time after the murder of the Waynes, Harvey tied his father up and left him trapped in their house for days until the police finally found him. Harvey was sent to an Arkham boys rehabilitation home upstate where he first met Bruce Wayne, having been sent to the home too to better handle his grief. The boys became good friends but wouldn't realize their identities until years later.

The boys made a pact that someday they'd each kill the other's enemy - Harvey would kill Joe Chill, and Bruce would kill Harvey's father. However, while Harvey was at the home, his father attempted to turn over a new leaf and melted down his coin, reminting it into a coin with only two-heads as a symbol that he would never beat Harvey again. Harvey backed out his deal with Bruce, choosing to give his father a second chance, a choice Bruce found to be incredibly naive. His hard work ethic, however, allowed him to rise to become a lawyer.

Early Career
As a young man, Dent became an incredibly skilled defense attorney for criminals in Gotham and began making a name for himself in the city. Harvey was introduced to his future wife Gilda Gold by Bruce Wayne at one of his parties, who believed that the two would have chemistry.

Some time later after the first appearance of Batman, Harvey and Gilda were married, and Dent had become one of the best defense attorneys in Gotham, having successfully exonerated some of the criminals Batman had caught. Because he felt that Dent's talents could be better applied to the right side of the law, Bruce Wayne suggested Harvey become Gotham's district attorney, to which Dent agreed and he was later awarded the position.

Harvey Dent was a great district attorney, leading a crusade against the filth and corruption in Gotham he had previously defended. Batman, Commissioner Gordon, and Dent worked closely together during Batman's second year in order to dismantle the gangs and organized crime in their city.

Bruce Wayne and Harvey Dent would together attempt to reopen the Arkham rehabilitation home where they first met, but their plan eventually fell apart.

In one of Dent's last cases as district attorney, he lost against a mercenary named Karl Twist due to some GCPD officers misplacing substantial evidence that would have put the man behind bars. This loss would remain as a bitter memory with Dent for years. He was nicknamed "Apollo" by the media, because he was charming, good-looking and seemingly untouchable. He was dedicated to his job of upholding law and order, and became one of the first supporters, allies and even friends of the Batman.

The Long Halloween
At the time of his job as D.A., the worst criminal threat in Gotham was the nigh omnipotent mafia boss, "The Roman." After Dent struck several blows to the Roman's Empire, Falcone hired to eliminate the D.A. However, the attempt by Mickey's gang to take out Dent failed. He forged a triumvirate with Batman and Commissioner James Gordon to bring the man down within the law, no matter what the cost. His slightly angrier temperament led Batman and Gordon to distrust him slightly, believing there was a possibility he might be the mysterious "Holiday" killer who was gunning down mob members at the time (including Mickey and his gang). The alliance ended tragically when Sal Maroni, believing Dent to be responsible for the death of his father, threw acid in his face during a trial. Dent was horribly scarred on the left side of his face.

Dent escaped from the hospital and descended into madness. He became obsessed with duality and opposites, and developed a second persona, the villainous Two-Face, to compliment the law and order obsessed Harvey Dent. As Two-Face, his trademark was crimes involving the number two. His obsession even shows in his clothes, which are usually composed of two halves made out of very different materials. He carries a double-sided coin with one side scratched at all times.

His first crime as Two-Face was the killing of his corrupt Assistant District Attorney Vernon Wells and Carmine Falcone. (Two-Face failed to kill Maroni, as he had already been assassinated at this point by Falcone's son Alberto.) Two-Face was eventually incarcerated in Arkham Asylum.

Two-Face next escaped from Arkham Asylum on the following Halloween (possibly aided by Maroni's twin sons Pino and Umberto), stole his old case files, and began the dismantling of the Falcone crime family. A new killer began following The Holiday's pattern, only this time not killing mobsters but cops. Dent saved Jim Gordon from the Hangman, as the new murderer was dubbed, and told Gordon he was not the Hangman. He continued using his alliance to the rest of Batman's Rogues Gallery to dismantle the mob. It was during this time he was having an affair with his successor as District Attorney, Janice Porter, a person he used to meet back at Gotham University when he was a professor. Porter was soon killed by Two-Face when she said she loved him. Over the the course of the year, he finally succeeded in eliminating Carmine Falcone's successor, his daughter Sofia Gigante Falcone who was revealed to be the Hangman the entire time, and even though he was taken in, Two-Face had permanently shifted the balance of power in Gotham's underworld from the mob to the so-called "costumed freaks."

Early Crimes
Some point after he became Two-Face, Dent tracked down his abusive father and had him kept alive, tied up for years, in a hidden location in Reno.

Two-Face would later join the War of Jokes and Riddles, choosing to join the Riddler's army against the Joker. After weeks of fighting, Batman finally managed to contain the fight, and Two-Face was simultaneously apprehended with the rest of Riddler's army.

Sometime after the death of the second Robin Jason Todd, Two-Face, having escaped prison, captured both Batman and Nightwing until he was stopped by the then-untrained Tim Drake; the successful rescue would go on to convince Batman to take Drake as his third Robin.

History with "The Boy Wonder"
Two-Face was the reason Bruce Wayne fired Dick Grayson, then Robin, from being his partner. After a failed attempt to rescue the then D.A. from Two-Face, who also had The Dark Knight captive as well, Two-Face brutally beat Dick, scaring Batman into firing Dick.

Later, Two-Face killed a henchman by the name of Willis Todd who happened to be the father of Jason Todd, the second Robin. In the wake of Todd's career as Robin, Two-Face came in conflict with the new Boy Wonder, who helped Batman put an end to Dent's new criminal spree.