不 - negative, non-, bad

disquieting; threatening; turbulent; restless; unsettled; disturbing

impossible

sudden; abrupt; unexpected; unforeseen

wrong; bad; improper; unjustifiable; inadvisable

incomprehensible; mysterious; inexplicable; inscrutable; enigmatic; baffling

indispensable; essential

heart failure

lack of sleep; insufficient sleep

lack of filial piety; disobedience to one's parents

misfortune; bad luck; ill luck; ill fortune

anxiety; uneasiness; worry; apprehension; fear; insecurity; suspense

displeasure; discomfort; unpleasantness