1) Anxious one 2) Chicken Little 3) Chicken little, notably 4) Communicator 5) Cousin of a crapehanger 6) Fear spreader 7) One who cries wolf 8) Overreacting sort 9) Panic-button pusher 10) Panicky person 11) Scaremonger Found on https://www.crosswordclues.com/clue/alarmist
A·larm'ist noun [ Confer French alarmiste .] One prone to sound or excite alarms, especially, needless alarms. Macaulay. Found on http://www.encyclo.co.uk/webster/A/49