Complete Monster/The Bible

Even the holiest of books is not devoid of some of the worst Complete Monsters of literature, or at least that's how they're commonly interpreted.

Satan

 * Known as the Devil, the Accuser and Prince of Lies, Satan is no doubt one of the Trope Codifiers of the Complete Monster trope itself, given his origins within religion and history as the ultimate Big Bad and The Corrupter of Mankind and the father and master of all Demons.
 * Once a prideful and beautiful Seraph (Archangel or Cherub in some texts) named Lucifer, he arrogantly believed he was better than humanity and refused to bow down to them, which led to him being cast down by the Archangel Michael for attempting to usurp God.
 * In the Old Testament, Satan as the Serpent introduced sin into the world by tempting Adam and Eve to eat the forbidden fruit in the Garden of Eden just to spite God. Satan then through God's permission is allow to try and break Job's faith in God by torturing the poor man by making him terribly ill, slaughtering his loved ones and turning his friends against him while also destroying his lands and crops in order to make him turn against God.
 * Within the New Testament, Satan corrupts Judas Iscariot and makes him betray Jesus of Nazareth and hand him over to the Romans, in which he attempts to corrupt Jesus himself and offer him the world as his kingdom so long as he worships him instead of God. In Revelations, Satan initiates The End of the World as We Know It, conquering the planet and bringing mankind to its knees by releasing the Seven Seals which brings forth the Four Horsemen of the Apocalypse and the Great Beast, Satan's regent on Earth who conquers the world in the name of Satan and forces people to bear his mark and pray to his statue, under threat of execution if they don't agree to do so, yet sending those who agree to Hell, ensuring that mankind will suffer regardless.

Other Examples

 * Haman, from the Book of Esther of the Judeo-Christian Myth. A Treacherous Advisor who plots the genocide of the Jewish people simply because he felt offended by one Jew's refusal to bow to him, he is arguably the worst human villain in Biblical literature. And his Xanatos Backfire at the gallows he had planned for Mordecai was also quite spectacular, especially after he went to King Ahasuerses to talk him into having Mordecai hanged (never getting around to it due to an unrelated matter) and wound up instead feting Mordecai for his heroism in saving the king's life from a couple of rebellious eunuchs--which wound up being the point where even his wife told him to his face that his obsession with killing the Jews would become self-destructive real soon. Naturally, he ignores her and goes ahead with his plans to wipe out the Jews. His name has become a watchword for anti-Semitism and he is viewed in rabbinical tradition as an archetypal evil figure.
 * Antioch from the Maccabees book. The terrible tortures he and his people subject a whole Jewish family to (seven teenage boys and their mother) are pure Nightmare Fuel, to the point where the author himself, after writing about how the family was boiled alive for their faith, actually said, "As for the rest of the martyrs who fell because of Antioch's killing spree against the Jews, need I say more?"
 * Goliath of the Philistines is described as being an almost literal monster of a man who is devoid of humane qualities and spoke blasphemy against God any chance he got. He also enjoyed killing a lot of people.
 * Jezebel wasn't a very nice customer either, being a sociopathic princess who married a king and manipulated him into abandoning his faith in favor of worshiping evil deities Baal and Asherah. She had most of God's prophets killed in torturous, agonizing ways, tried to kill Elijah, and crossed the Moral Event Horizon by fabricating incriminating evidence against an innocent, righteous man named Naboth in order to have him stoned to death, simply because her husband wanted his vineyard! Let's just say her Disney Villain Death (which she ordered to happen during her Villainous Breakdown) was well deserved.
 * Herod the Great. We know from secular histories that he was a paranoid SOB who murdered his own sons when he suspected them of plotting against him and was, in fact, responsible for many massacres. Why do secular historians not cover the massacre of the infant boys in Bethelehem? For him, it was just another day, another possible threat dealt with. Or because there are no other records at all about this event - either because, like the census, that isn't mentioned by any Roman records, it was made up to add some glamour to Jesus' infancy, or because Bethlehem was so small a village that very few children would have been killed in the event and not enough people wrote about it to provide us with surviving records.
 * Herod knew that nobody would mourn his death after he killed every infant in Bethlehem with extreme prejudice, so he ordered every Jewish priest killed like those infants on the day he died--just so there would be mourning in the land, all right--in a Thanatos Gambit which was ultimately never carried out.