"I would agree with MrsLulu's point about Satan. As to his being created. Well, yes and no. He was created a perfect angel, but he made himself Satan. This descriptive name was given to him because of his taking a course of opposition and resistance to God. Just as a child is not born a thief, he makes himself a thief so to with Satan. He was not created Satan, he chose to become an opposer of God."
To be clear, I don't believe Satan (or God) exists. But if you're using the Bible as a source on their respective characters, then Yahweh kills condsiderably more people (at the very least 2.5 million) than Satan (10 - most of whom he is instructed to kill by Yahweh.)
The objection is simple. We don't claim God exists, or that he is responsible for tsunamis. We're just questioning whether the world as we know it is consistent with the idea of an omnipotent, omniscient, omnibenevolent creator. The proposition that the world exists alongside such a being is so full of holes that it ought to be rejected by any right-thinking person - and is in fact rejected by several theologians (albeit not by many an average believer).