In episode 24, we finally see the face of the much spoken of mother of the Saima Demons, Grand Witch Grandienne. At first she has an expression of bored contempt, but then she starts grinning, revealing very large, very sharp teeth, and her eyes grow wider and start glowing until you can't see her irises anymore. It should not be possible for a face to be that scary.
In the opening sequence, there's a bit with the planet being smashed by two demonic hands. It's narmish for an adult but go tell this to a kid and see what they think.