noun
top gun; big cheese; top dog
Slangy loanword for a top performer, ace, or the most important person in a group. Often used in business, sports, or competitive contexts.
彼は営業部のトップガンだ。
He's the top gun in the sales department.
あの選手はチームのトップガンとして活躍している。
That player is performing as the team's top gun.