also: ひとりでんか
noun
sole mastery; reigning supreme; unchallenged dominance
Describes a situation where one person has complete control or influence, with no rivals. Often used in contexts like business, politics, or personal relationships.
彼は会議で一人天下だった。
He dominated the meeting unchallenged.
あのチームはリーグで一人天下の強さだ。
That team reigns supreme in the league.