Killers often rise to the top, but to do so they need a polluted environment. Corruption of the political, corporate or social systems can create the conditions in which killers thrive. Once in power they are ruthless and difficult to remove.
Killers often believe they are working for a greater social good, and in many cases their initial motivation and actions appear to bear this out.
Romania's Nicolae Ceausescu began his political career fighting fascists during the Second World War and in the initial years of his dictatorship appeared to be steering his country to independence and prosperity. Indonesia's Suharto was successful in holding together his highly diverse and factious nation at a particularly vulnerable time. Even Adolf Hitler's regime initially brought stability to a society in danger of complete collapse.
But such killers always foul their achievement with the toll of their excess.
Other killers can only be described as purely bad - self-serving, ignorant and corrupt. Uganda's Idi Amin did nothing for his country except inflict terror and destruction. Efraín Ríos Montt, Guatemala's Bible-bashing despot, was just another in that country's long line of murderous presidents. Burma's Ne Win and his cohorts turned a country full of promise into one of the world's most downtrodden and poor.
A common trait of all the killers featured here is their unwavering belief in the rightness of their acts, if not those act's complete righteousness. None of those who are now dead went to their graves with any sense of guilt or regret, and it is unlikely that any of those still living will. World-class killers are always loaded with hubris; an overweening belief in their own infallibility. They are paternalistic and proud. It is no coincidence that they are all men, just as it is no coincidence that they scorn democracy.
The extent to which killers are products or reflections of their societies should also not be overlooked. Just as heroes are icons of movements for social justice, killers are a distillation of the darkness on the outskirts of society that at times of stress seeps to the core.
Adolf Hitler was a master at playing on the underlying antisemitism that was endemic in Germany between the world wars. Serbia's Slobodan Milosevic never hesitated to exploit the historic distrust between the populations of Croats, Serbs, Muslins and Christians in Yugoslavia. Japan's Prince Yasuhiko Asaka was a symbol of the havoc that can be wrought when imperialism and militarism converge.
This site provides a personal selection of killers from the 20th Century. The facts are as accurate as could be determined from credible sources available on the internet and elsewhere. The interpretation is entirely personal. It always is.