Vicious. (adjective) unpleasantly fierce, nasty; dangerous; malicious
When the word came into English, in the 14th century from French, it preserved the literal sense of "relating to vice", and generally meant "immoral, depraved". There is just one use of this in Shakespeare, when Cordelia asks her father to say that his displeasure at her is not because of any "vicious blot, murder, or foulness" (King Lear, I.i.227). Otherwise we get two derived senses. One is "defective, bad, wrong", as when Hamlet talks of men who have "some vicious mole of nature in them" (Hamlet, I.iv.24) or Iago says "I perchance am vicious in my guess" (Othello, III.iii.144). The other is "blameworthy, shameful", as when Cymbeline says, of his Queen, "It had been viciousTo have mistrusted her" (Cymbeline, V.v.65). The modern sense of "nasty to the point of physical attack" began in relation to animals, in the 18th century. There is no hint of this in Shakespeare. When we hear Adriana talking of her husband as "vicious, ungentle, foolish, blunt, unkind" (The Comedy of Errors, IV.ii.21), she is not suggesting that he beats her.