extremely; in the extreme; knows no bounds (e.g. rudeness); unparalleled
boundless (e.g. universe, ocean); limitless
彼の態度は失礼極まりない。
His attitude is extremely rude.
昨冬の登山道は危険極まりなかった。
The mountain trail last winter was extremely dangerous.
その騒音は不愉快極まりなく、私は部屋を出た。
The noise was extremely unpleasant, so I left the room.