@Underconstruction It's in the story. God is saying what a great servant Job is, and the devil says "let me kill his family and we'll see if he still worships you." God says OK, so the devil kills Job's entire family and servants except for one guy.
I'm not saying this actually happened, it's just a story, but if you're asking where in the fictional Bible does the devil character kill other characters, it's in the Book of Job.
@Underconstruction Yes, the God character is much worse. This is why the Gnostic Christians believed that the God of the Bible was an evil demiurge named Yaldabaoth, who was the son of Wisdom, which had itself been created by the true God. So their goal was to get past the evil God of the Bible and know the one true God above him. This sect was suppressed when the much simpler Christianity of Paul took hold.
