also: ワンマンショウ
noun
Refers to a performance or event dominated by a single person, often used literally for a solo stage act or figuratively for a situation where one person does everything.
彼のワンマンショーは大成功だった。
His one-man show was a great success.
会議が社長のワンマンショーになってしまった。
The meeting turned into the president's one-man show.