(n.) An implacable or malicious foe; one who is diabolically wicked or cruel; an infernal being; -- applied specifically to the devil or a demon.

Apollyon Baba Yaga Beelzebub LSD user Lilith Lucifer Mafioso Old Nick Old Scratch Satan Young Turk acidhead addict aficionado afreet alcoholic ape-man barghest beast beldam berserk berserker bigot bomber brute buff bug cacodemon chain smoker cocaine sniffer cokie collector cubehead daeva demon devil devil incarnate devotee diablo dipsomaniac dope fiend doper dragon drug abuser drug addict drug user drunkard dybbuk eager beaver energumen enthusiast evil genius evil spirit faddist fan fanatic fiend from hell fire-eater firebrand follower freak fury genie genius ghoul glue sniffer goon gorilla great one for gunsel gyre habitual hardnose harpy head heavy smoker hell-raiser hellcat hellhound hellion hellkite hobbyist holy terror hood hoodlum hophead hothead hotspur hound hype incendiary incubus infatuate jinni jinniyeh junkie killer lamia mad dog madcap maniac marijuana smoker methhead monster mugger narcotics addict nut ogre ogress pillhead pothead pursuer rakshasa rapist revolutionary rhapsodist satan savage serpent she-wolf shedu snowbird speed freak spitfire succubus sucker for termagant terror terrorist the undead tiger tigress tough tough guy tripper ugly customer user vampire violent virago visionary vixen werewolf wild beast witch wolf yogini zealot