All narcissists are self-obsessed, but malignant narcissists are at the top of the scale. They have a pathological self-belief--a sense of grandiosity, even--which demands attention and admiration. They're convinced they're special in some way and want other people to acknowledge it as well. Crucially, they're also sadists who lack any conscience. They don't necessarily get fulfilment from inflicting pain, but they enjoy the sense of power it gives them. And they're indifferent to any suffering they might cause.