Frank Castle wasn't born the Punisher. He was made; built piece by piece into the hardest man the world has ever known. The seeds of the man he is were always there, of course. Even as a child he had a stubborn streak a mile wide, and an almost sneering disregard for those he saw doing wrong. Trained by the military to the peak of physical capacity, and schooled in the most advanced tactics of modern warfare science, his service made him a master of weapons and combat while his experience taught him a singularity of vision that allows him to cope with the realities of war. The brutal slaughter of his family was only the last brick in the edifice. What was needed, Castle saw, was someone capable of punishing the guilty for their crimes.
The Punisher isn't interested in right and wrong. He isn't interested in rehabilitation or peace. He isn't concerned with the rule of law, the protection of property or the sanctity of freedom. He's interested in one thing, and one thing only: the guilt of the man in his crosshairs.