inflexibility vs unadaptability

inflexibility and unadaptability both are nouns.

Word	Noun	Adjective	Verb	Adverb
inflexibility	Yes	No	No	No
unadaptability	Yes	No	No	No

As nouns, unadaptability is a hypernym of inflexibility; that is, unadaptability is a word with a broader meaning than inflexibility:

inflexibility: the quality of being rigid and rigorously severe
unadaptability: the inability to change or be changed to fit changed circumstances

inflexibility (noun)	unadaptability (noun)
the quality of being rigid and rigorously severe	the inability to change or be changed to fit changed circumstances
a lack of physical flexibility