How would you have evil if no Satan?

So many want to disbelieve in God so does that mean they do not believe in Satan also? And if there is no Satan how can there be evil? How can anyone coin the moniker of evil on people like Charles Manson, Saddam Hussain, Tommy Lee Searl, Richard Ramirez, etc.? Killers would be just part of the landscape, they would be no different than the croc that lies under the water in the river taking down the weak, young, and sick wildebeest. The wildebeest hold no grudge or have a need for vengeance anymore than the croc killed for the trill of it. Death was death, and attack was just part of the daily biz. Where would evil come from if not from Satan and how would you have Satan if no God?