every one (without exception); all of them; to a person; to the last person
参加者は一人残らず名簿に名前を書いた。
Every participant wrote their name on the roster.
掃除は一人残らず手伝ってください。
Please have everyone help with the cleaning; not a single person should be left out.
彼の冗談は一人残らず笑わせた。
His joke made everyone laugh without exception.