reluctance vs unwillingness

reluctance and unwillingness both are nouns.

Word	Noun	Adjective	Verb	Adverb
reluctance	Yes	No	No	No
unwillingness	Yes	No	No	No

As nouns, unwillingness is a hypernym of reluctance; that is, unwillingness is a word with a broader meaning than reluctance:

Other hypernyms of reluctance include involuntariness.

reluctance (noun)	unwillingness (noun)
a certain degree of unwillingness	the trait of being unwilling
(physics) opposition to magnetic flux (analogous to electric resistance)