Incompetence; inability or inefficiency — lacking the ability to perform duties or tasks.
あの部署は無能な管理のせいで混乱している。
That department is in chaos because of incompetent management.
無能さが露呈すると信頼を失うことがある。
When incompetence is revealed, one may lose trust.
An incompetent person — used (often disparagingly) to describe someone lacking ability.
彼は何度注意しても改善しないので、周りは彼を無能だと思い始めた。
Even after repeated warnings he doesn't improve, so people began to think he was incompetent.
無能な上司の下で働くのはストレスが多い。
Working under an incompetent boss is very stressful.