2. Frank Castle (The Punisher)
Frank Castle is a man with nothing to lose. Such people are often the most dangerous which combined with his years of training in guerilla warfare make him easily one of the most dangerous men in the history of the comics medium. After his family were brutally slain by the mob (depending on the version of events you follow) Frank Castle transformed himself into the mysterious Punisher figure in an attempt to exact his own brand of justice against the people who ruined his life. Soon The Punisher is a wanted man himself as his vigilante actions fall foul of the police. With many of the mob members dead Castle is unable to return to his former life and thus remains as The Punisher cleaning up the streets one hood at a time. Unlike most Marvel heroes at the time Punisher was happy to kill people which meant he was too dangerous for the mainstream publications. As a result he would feature within his own stories inside the general canon but with only occasional crossovers with less adult oriented stars. Over the years Frank Castle has slowly become more deranged seeing himself in some issues as God's personal tool for punishment on the Earth. Deluded though he may be he is no less dangerous and as each day passes that he eludes capture he becomes a bigger threat to the criminal element.