ability:
inadequacy,
incompetence,
inability,
stupidity,
ignorance,
clumsiness,
weakness,
inanity.
convenience:
inconvenience,
uselessness,
unsuitability,
inexpedience,
waste,
inutility.
dexterity:
awkwardness,
ineptness.
knack:
lack,
want,
ineptitude.
readiness:
discouragement,
unpreparedness.
skill:
incapacity,
inexperience,
incapability.