unavoidable casualty vs tragedy

unavoidable casualty and tragedy both are nouns.

Word	Noun	Adjective	Verb	Adverb
unavoidable casualty	Yes	No	No	No
tragedy	Yes	No	No	No

As nouns, tragedy is a hypernym of unavoidable casualty; that is, tragedy is a word with a broader meaning than unavoidable casualty:

unavoidable casualty: a natural and unavoidable catastrophe that interrupts the expected course of events
tragedy: an event resulting in great loss and misfortune

Other hypernyms of unavoidable casualty include calamity, cataclysm, catastrophe, disaster.

unavoidable casualty (noun)	tragedy (noun)
a natural and unavoidable catastrophe that interrupts the expected course of events	drama in which the protagonist is overcome by some superior force or circumstance; excites terror or pity
	an event resulting in great loss and misfortune