極まる・極まりない|きわまる・きわまりない

1. 1極まりない: states that something is extremely or utterly so, typically as a harsh criticism of behavior, attitudes or ideas.Ex. 1
2. 2極まる: carries the same 'to the extreme' meaning and is somewhat less common than 極まりない.

The pattern is written and formal in tone. It appears in criticism, commentary and news-style writing to condemn something as extremely rude, dangerous, foolish and so on. It typically delivers an emphatic evaluation of a person, act or situation rather than simply voicing the speaker's feelings, though words such as 不安 can also appear with it.

• の極みN1「の極み」attaches to nouns and can be used for both positive and negative evaluations, often expressing strong feelings such as 「感激」 or 「光栄」; 「極まりない」attaches to na-adjective stems and is mostly used for negative evaluations. When evaluating things like 「無責任」 or 「贅沢」, the two can be interchangeable.
• の至りN1「の至り」uses 「名詞＋の」 and appears mostly in speeches and apologies, expressing the height of gratitude, unease/being overwhelmed, or self-reproach, as in 「光栄の至り」; 「極まりない」attaches directly to na-adjective stems and mostly gives negative evaluations, so the two are generally not interchangeable.
• 限りだN1「限りだ」expresses the speaker's own strong emotions and can attach to i-adjectives, 「な形容詞＋な」, or 「名詞＋の」; 「極まりない」attaches directly to na-adjective stems and is mostly used for harsh evaluations of others or of situations. The two are close in meaning only when expressing one's own feelings such as 「残念」.
• といったらないN1「といったらない」can be used for both praise and criticism, attaches to nouns, adjective stems ＋さ, or i-adjectives, has a neutral register with a strong exclamatory flavor, and is often used when recounting things one has seen or heard; 「極まりない」attaches to na-adjective stems, is stiff and literary, and is mostly used for negative evaluations.
• んばかりにN1「んばかりに」attaches to the negative stem of a verb and is a hyperbolic metaphor indicating that someone looks about to perform an action, or, as in 「と言わんばかりに」, that an attitude clearly conveys a certain meaning; 「極まりない」attaches to na-adjective stems and directly evaluates a quality as reaching its extreme, so the two cannot be interchanged.
• てたまらないN2「てたまらない」mostly expresses the speaker's own emotions or physical sensations, can attach to adjectives or verbs, and has a neutral register; 「極まる」「極まりない」attach to na-adjective stems or 「…なこと」, are stiff and literary, and are mostly used to harshly evaluate someone's behavior or a situation.

極まる／極まりない attach directly to な-adjective stems or state nouns without の and mostly criticize. の極み and の至り follow a noun plus の and often express the height of emotion or honor (感激の極み, 光栄の至り). 限りだ, といったらない and てたまらない mainly convey the speaker's own feelings or sensations, while んばかりに means 'as if about to'.