Two-Face

Two-Face is one of Batman's well known enemies. He started out as a man called Harvey Dent who at 26, was the youngest district attorney ever to serve Gotham City, and is nicknamed "Apollo" for his good looks and clean-cut image. He is elected about six months before Batman begins his war on crime. For a time, Gordon speculated that Dent might have been Batman, but eventually dismissed him as a candidate as Dent lacked the Batman's financial resources even if he possessed his desire for justice. Falcone hires the corrupt Assistant District Attorney Fields to disfigure Dent with sulfuric acid. Two-Face gets his trademark coin from his abusive father, who would employ the coin in a perverse nightly "game" that would always end with a beating. This would instill in Dent his lifelong struggle with free will and his eventual inability to make choices on his own, relying on the coin to make all of his decisions. He is a deadly villain that shoots you if the coin lands on the tails (which is also scarred). He has also followed many fights with the Dark Knight making him one of Batman's well known villains.

Two-Face has appeared in most of Batman's animated TV series and movies. The most well known actors who played him in movies are Tommy Lee Jones (Batman Forever) and Aaron Eckhart (Dark Knight). Aaron Eckhart was the most notable playing Two Face in the Dark Knight with a different origin story. In this movie version he is Gotham's symbol of hero against criminals and he proposed the "Dent Act" that stopped most of Gotham's criminal violence and actions. He also became the Joker's main target and made a search for him. Harvey was also allied with Batman and even saying that he is Batman to cover Batman's identity. Harvey is kidnapped by Joker along with Rachel Dawes (his girlfriend) and tied up in two different buildings with each having a bomb installed that is about to explode. Harvey struggled to get untied and fell with a tank of oil which wet the left part of his face until Batman rescued him and the bomb exploded dropping fire on him and the oiled part of his face got cached on fire burning the left part of his face. Rachel died and Harvey (now Two-Face) kills the police that he believes are the responsible ones for Rachel's death using the coin to make the decisions for him. He died at the end of the film.
It is unknown whether he would appear in any future Batman (Rebooted) films.