For I will be to Ephraim like a lion, And like a young lion to the house of Judah. I myself will tear in pieces and go away. I will carry off, and there will be no one to deliver.
When they offer their sacrifices unto the gods in the Northern Kingdom they would do it with great flare. Again, trying to make a big deal out of it so all of the people would be in awe. So that is what is meant by "profound to make slaughter."