Satanism.

Satan = Adversary
Satanism = Adversing [Christianity]
Sadism (very similar word, and you must remember people's general illiteracy) = derivation of pleasure from inflicting pain on others.
Also, Satan is not necessarily innately evil, of course. Just the adversary.

I think we should consider the Satanic/Byronic hero of the Romantics.The Norton Anthology of English Literature: The Romantic Age: Topic 1: Explorations

Not until the age of the American and French Revolutions, more than a century after Milton wrote Paradise Lost, did readers begin to sympathize with Satan in the war between Heaven and Hell, admiring him as the archrebel who had taken on no less an antagonist than Omnipotence itself, and even declaring him the true hero of the poem. In his ironic Marriage of Heaven and Hell (NAEL 8, 2.111-20), Blake claimed that Milton had unconsciously, but justly, sided with the Devil (representing rebellious energy) against Jehovah (representing oppressive limitation). Lecturing in 1818 on the history of English poetry, Hazlitt named Satan as "the most heroic subject that ever was chosen for a poem" and implied that the rebel angel's Heaven-defying resistance was the mirror image of Milton's own rebellion against political tyranny. A year later, Percy Shelley maintained that Satan is the moral superior to Milton's tyrannical God, but he admitted that Satan's greatness of character is flawed by vengefulness and pride.
It was precisely this aspect of flawed grandeur, however, that made Satan so attractive a model for Shelley's friend Byron in his projects of personal myth-making. The more immediate precedents of the Byronic hero-a figure that Byron uses for purposes both of self-revelation and of self-concealment-were the protagonists of some of the Gothic novels of the later eighteenth century. Examples are Manfred, the ominous hero-villain of Horace Walpole's The Castle of Otranto (1764) (NAEL 8, 2.579-82) and the brooding, guilt-haunted monk Schedoni of Ann Radcliffe's The Italian (1797), who each embody traits of Milton's Satan.

Not on Christmas!