Sidekicks? Opposites?

David’s life was very full of adventures and different things. One thing about the text which really stood out to me was this on Samuel 19-9. “And the evil spirit from the LORD was upon Saul.” The evil spirit from the LORD? In The Bible they have always described the LORD God as almighty, as wonderful, incredible who always wants the best for his sons. To hear about his evil spirit is quite shocking. Besides you might have heard about the devil may be as his opposite. Now I make the connection to Gilgamesh, is there a sidekick for the LORD? I have seen sidekicks for Moses and even for David but I would say the LORD doesn’t have a sidekick. But does he have an opposite? Or something in him that is not perfect?