bad blood vs hostility

bad blood and hostility both are nouns.

Word	Noun	Adjective	Verb	Adverb
bad blood	Yes	No	No	No
hostility	Yes	No	No	No

As nouns, hostility is a hypernym of bad blood; that is, hostility is a word with a broader meaning than bad blood:

Other hypernyms of bad blood include enmity, ill will.

bad blood (noun)	hostility (noun)
a feeling of ill will arousing active hostility	violent action that is hostile and usually unprovoked
	a hostile (very unfriendly) disposition
	the feeling of a hostile person
	a state of deep-seated ill-will