If you count up how many people God killed written in the Bible, it comes to exactly 2,476,633. That excludes deaths like those in the flood, where actual statistics aren't given, so it isn't just some estimate, although is well below the total death count because of not involving these.
The Devil killed 10. That's it. And those were with God's permission, in the story of Job, where he killed Job's family, as part of a bet with God.
If you included estimates for their killing sprees where specific numbers aren't given, Satan's total goes up to a slightly impressive 60. Still nothing on God's total, and if you added estimates for the flood, various plagues, and the mass murder of the peope of Sodom and Gomorrah, his total goes up to roughly 25 million. You have to ask if that means Satanists are just worshipping the lesser of 2 evils.
So yeah you're right. Something really doesn't add up there. On the logic that mass murder is evil, Satan's the better guy.