While there's no such thing as a "good" killer, there are some examples of fictional murderers who tend to lean towards the more ethically sound end of the moral scale. Superhero vigilantes are a good example of this, as are soldiers or mercenary figures who fight on the side of the "good guys".
One of the most famous serial killer protagonists, of course, has to be Dexter Morgan - a sociopath who only targeted people he knew were guilty of murder. But it turns out his crimes are a little closer to real-life than many fans of the show probably suspected.
Pedro Rodrigues Filho, a Brazilian man who is more commonly known by the nickname Pedrinho Matador (Killer Petey), has at least 71 confirmed murders to his name - but the vast majority of his victims were actually criminals themselves.
The serial murderer claims that he first realized he had an urge to kill when he was just 13-years-old. The young teenager had become involved in an argument with an older cousin, during which he pushed the boy - causing him near-fatal injuries in the process. Sure enough, a year later he acted upon his desire, and killed the Vice Mayor of the town of Alfenas because the man had fired his father. Shortly after that, he also took out a school guard who he believed to be a thief (but who might not have been), and then another guard - supposedly the real thief.
After that, he moved to Sao Paulo, where he continued his criminal streak by committing a speight of burglaries and murdering a drug dealer. While there, he lived with Maria Aparecida Olympia, a woman who tragically met her end at the hands of gang members. In order to avenge her, Filho tortured and killed several people in order to find out the identity of her murderers.
By the age of 18, he had already racked up a death toll of 10 people - but his rampage was only just beginning.
Filho's next target was his own father, who was spending time in prison for the murder of Filho's mother. The man had a history of domestic violence against his wife, and had actually caused damage to Filho's skull when he was still in the womb, but their tumultuous relationship came to an end when he attacked her with a machete.
So, again, as an act of revenge, Filho took out the criminal. He visited him in jail, where he proceeded to stab him 22 times. After murdering his own flesh and blood, Filho cut out a piece of his father's heart, chewed it, then threw it away.
He was finally arrested shortly before his 20th birthday, but - in true Filho style - even the story of his apprehension is an unbelievable one. Reportedly, the serial killer was placed in a police car along with two other criminals who were being taken in under arrest, one of whom was a known rapist. By the time the police officers had rolled up to jail and open the back doors to check on their suspects, Filho had killed the rapist.
He was then incarcerated in a seemingly low-security prison, as, while there, he managed to kill 47 of his fellow inmates. It's been reported that the convicts Filho went after were the ones whom he felt deserved retribution.
Now, with a kill record of anywhere up to 100 people to his name, you'd expect Filho to have been locked up in isolation and the key thrown away - but that's not how this story ends.
Originally, the murderer was sentenced to 128 years in prison, with the subsequent murders he committed there extended this to 400 years. However, according to Brazilian law, the maximum prison sentence a person is allowed to serve is just 30 years. Filho ended up serving an additional four for the murders he committed behind bars, but was eventually released in 2007.
He is currently 63 years old, and has vowed to kill other criminals if he gets the chance.