hard knocks vs misfortune

hard knocks and misfortune both are nouns.

Word	Noun	Adjective	Verb	Adverb
hard knocks	Yes	No	No	No
misfortune	Yes	No	No	No

As nouns, misfortune is a hypernym of hard knocks; that is, misfortune is a word with a broader meaning than hard knocks:

Other hypernyms of hard knocks include bad luck, ill luck, tough luck.

hard knocks (noun)	misfortune (noun)
a state of misfortune or affliction	unnecessary and unforeseen trouble resulting from an unfortunate event
	an unfortunate state resulting from unfavorable outcomes