The old adage of Epicurus:

Is God willing to prevent evil, but not able? Then he is not omnipotent.
Is he able, but not willing? Then he is malevolent.
Is he both able and willing? Then whence cometh evil?
Is he neither able nor willing? Then why call him God?

So does the existence of Evil negate the existence of a God? Does it make him a malevolent God?
When God was finished creating the world he remarked that "It was good" but can evil be classified in this? The yang to good's ying? Balancing the equation out? Yet why does their appear to be more evil than good in the world? Why does so much evil go unpunished and so much good unappreciated?