bitterness vs enmity

bitterness and enmity both are nouns.

Word	Noun	Adjective	Verb	Adverb
bitterness	Yes	No	No	No
enmity	Yes	No	No	No

As nouns, enmity is a hypernym of bitterness; that is, enmity is a word with a broader meaning than bitterness:

Other hypernyms of bitterness include hostility, ill will.

bitterness (noun)	enmity (noun)
the property of having a harsh unpleasant taste	the feeling of a hostile person
a rough and bitter manner	a state of deep-seated ill-will
the taste experience when quinine or coffee is taken into the mouth
a feeling of deep and bitter anger and ill-will