I believe he's a character in a fairy tale (it was the big dragon image that helped me see that!), who, incidentally, killed less people than God in the Bible!
When I first read this sentence, it was like a lightbulb going off...you are all absolutely right...Satan gets villified by religions as the a convenient scapegoat to explain why suffereing exists. Satan only killed 10 people, with God's permission of course, so really, who is the most evil character in the Bible? If you equate murder and rape with evil, humans and God himself should be considered the most evil.