Incompetent
Part of speech: noun
Definition: A person who is incompetent.
Part of speech: adjective
Definition: Unskilled, lacking normally expected degree of ability. Unable to make rational decisions, insane or otherwise cognitively impaired.
Example sentence: Violence is the last refuge of the incompetent.
Inadequate
Part of speech: adjective
Definition: Not adequate; unequal to the purpose; insufficient; deficient; as, inadequate resources, power, conceptions, representations, etc.
Example sentence: The dogmas of the quiet past are inadequate to the stormy present. The occasion is piled high with difficulty, and we must rise with the occasion. As our case is new, so we must think anew and act anew.