incompetent
in-com-pe-tent
adjective
Lacking the necessary skill, ability, or knowledge to do something successfully.
"The new assistant proved utterly incompetent."
noun
A person who lacks the necessary skill or ability to do a task well.
"They dismissed him as an incompetent."
Thesaurus
Synonyms: unskilled, bad, feckless, unworkmanlike, ineffective, inept, inefficient, fumbling, bungling, clumsy, incompetent person, incapable
Antonyms: competent