1) Gratuitous 2) Groundless 3) Motiveless 4) Needles 5) Senseless 6) Unmotivated 7) Unwarranted 8) Wanton 1) Gratuitous 2) Motiveless 3) Unmotivated 4) Unnecessary 5) Wanton 
unprovoked 1. An attack, or a display of aggression or emotion; not caused by anything done or said. 2. Occurring without motivation or provocation; such as, an unprovoked attack.