Explanation
Expresses an extreme state, often negative; 'utterly', 'extremely', 'boundlessly'.
Formation
な-Adjective（語幹）+ 極まりない, い-Adjective（連用形）+ こと + 極まりない, Noun + の極まりない
Detailed explanation
The ～極まりない grammar point indicates an extreme or utmost degree, most commonly with a negative nuance (e.g., 失礼極まりない, 危険極まりない). It can sometimes be used for positive contexts, but that usage is less common.
Examples
彼の失礼な態度は極まりない。
Kare no shitsurei na taido wa kiwamarinai.
His rude attitude is utterly beyond words.
その運転は危険極まりない。
Sono unten wa kiken kiwamarinai.
That driving is extremely dangerous.
彼女のわがままぶりは非常識極まりない。
Kanojo no wagamama-buri wa hijoushiki kiwamarinai.
Her selfishness is utterly irrational.
この部屋の汚さは不衛生極まりない。
Kono heya no kitasa wa fueisei kiwamarinai.
The filthiness of this room is extremely unsanitary.
Practice
Grammar content sourced from hanabira.org.