unfitness

nouns

poor physical condition; being out of shape or out of condition (as from a life of ease and luxury)
is derived from
is derived from
antonym
lacking the power to perform
is derived from
the quality of not being suitable
"the judges agreed on his unfitness for the appointment"
is derived from
antonym
is a type of (narrower)
the quality of having the wrong properties for a specific purpose