Completely; entirely; without exception — often used when things all turn out the same way (frequently negative), somewhat formal or emphatic.
彼の提案はことごとく却下された。
His proposals were all rejected.
新しいレストランは、メディアの評価も客の評判もことごとく良かった。
The new restaurant received uniformly good reviews from the media and customers alike.
準備不足で失敗がことごとく重なり、プロジェクトは中止になった。
Due to lack of preparation, failures piled up one after another, and the project was canceled.