The first stories appearing in the Batman comic were written by Bill Finger and illustrated by Bob Kane, though Finger went uncredited for years thereafter. These early stories depicted a vengeful Batman, not hesitant to kill when he saw it as a necessary sacrifice. In one of the early stories, he is depicted using a gun to stop a group of giant assailants. the Joker, a psychopath who is notorious for using a special toxin that kills and mutilates his victims, remains one of the most prolific and notorious Batman villains created in this time period. During the period in 1940's and 50's when comic books began reflecting the patriotic views of Americans who supported the Allied efforts in World War II, the Joker was changed from cold-blooded murderer to playful trickster. Later, during the Silver Age, this type of super-villain changed from disturbing psychological assaults to the use of amusing gimmicks.
Typically, the primary challenges that the Batman faced in this era were derived from villains who were purely evil; however, by the 1970's, the motivations of these characters, including obsessive compulsion, child abuse and environmental fanaticism, were being explored more thoroughly. Batman himself also underwent a transformation and became a much less one-dimensional character, struggling with deeply rooted internal conflicts. Although not canonical, Frank Miller's The Dark Knight Returns introduced a significant evolution of the Batman's character in his eponymous series; he became uncompromising and relentless in his struggle to revitalize Gotham. The Batman often exhibited behavior that Gotham's elite labeled as excessively violent as well as antisocial tendencies. Miller portrayed him with an anti-heroic and near villainous characterization. This aspect of the Batman's personality was also toned down considerably in the wake of the DC-wide crossover Infinite Crisis, wherein Batman experienced a nervous breakdown and reconsidered his philosophy and approaches to his relationships. Currently, the Batman's attributes and personality are said to have been greatly influenced by the traditional characterization by Dennis O'Neil and Neal Adams's portrayals during the 1970's.