noun
unqualified person; incompetent person; square peg in a round hole
Formal term for someone who is not suited or lacks the necessary qualifications for a position or task. Often used in professional or evaluative contexts.
彼はその仕事には不適任者だと判断された。
He was judged to be unqualified for that job.
不適任者を重要なポストに置くべきではない。
You shouldn't put an incompetent person in an important post.
Compound of 不 (not), 適任 (suitable for a post), and 者 (person). The word is a straightforward Sino-Japanese formation.