Answer: knifer

AnswerCrossword Clue
KNIFERMacbeth, vis- -vis Duncan
KNIFERJack the Ripper, e.g.
KNIFERCertain attacker
KNIFERDangerous assailant
KNIFERAssailant without a gun
KNIFERMacbeth, to Duncan
kniferto stab with a knife
knifercutting instrument having a sharp blade in a handle
knifersomeone who knifes