kiss of death vs tragedy

kiss of death and tragedy both are nouns.

Word	Noun	Adjective	Verb	Adverb
kiss of death	Yes	No	No	No
tragedy	Yes	No	No	No

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

Other hypernyms of kiss of death include calamity, cataclysm, catastrophe, disaster.

kiss of death (noun)	tragedy (noun)
something that is ruinous	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