Two-Face

Harvey Dent was Gotham City's district attorney, but after being scarred for life, moved to a life of crime.

Biogrophy
Harvey Dent was a successful businessman and lawyer. One day he was defending Batman on charges of theft and murder. The prosecuter (a dreaded crimelord), seeing he was about to lose his case, threw toxic acid at Dent. Batman tried to rescue Dent, but was too late. From then on, half of Dent's face was horribly scarred.

Rivalries
Over the years, Two-Face had many rivalries with other DC characters, especially the following two:

Batman-- Although it was the crimelord's fault, Harvey had blamed Batman for his facial scarring. He and the Bat had fought each other in over 50 issues of Batman and Detective Comics.

The Joker-- It is unknown why the two supervillains hate each other. Maybe because they had rivarly in the past, perhaps when they were younger. Either way, these two always feud and compete on defeating Batman.

Facial Appearence
Two-Face's face has been altared over the years.

In Harvey Dent's first appearence in Detective Comics #66, the deformed portion of Dent's face is light green.

In the newer comics, as well as the motion picture Batman Forever, Dent's deformed part of his face is a bright red. As depicted in Batman:The Animated Series, it is a sky blue.