Although sometimes considered a hero, the Punisher is a savage and ruthless vigilante, who considers killing, kidnapping, extortion, coercion, threats of violence and torture as acceptable crime-fighting tactics. Driven by the deaths of his wife and children, who were killed by the mob when they witnessed a Mafia gangland execution in New York City's Central Park, Frank Castle wages a one-man war on the mob by using all manner of weaponry. A war veteran, Castle is a master of martial arts, stealth tactics, hand-to-hand combat, strategic planning and a wide variety of weapons.

Castle has since devoted his life to eradicating organized crime, using the nom de guerre of the Punisher, using his combat experience (four years as a United States Marine Corps Captain in a special operations unit in the Vietnam War), guerilla warfare (combat assault attacks, assassinations, ambushes, hit and runs, bombings, using the enemies' own money, weapons and supplies against them), urban warfare (using the crowded city of New York to blend in and disappear), psychological warfare (putting fear into the hearts of criminals), using detective-like skills (talking to people, reading obtained files on the people he goes after, tracking and surveilling the enemy), always adapting to the enemy such as using the Mafia's own methods and tactics against them (interrogating and torturing suspects to death in order to get information from them) and whatever resources and means may be necessary to do so, ranging from light anti-tank weaponry, to enraged polar bears, piranhas, and to a hydrogen bomb.