～て堪(たま)らないCan't help but want to, Very, Extremely

Both express intense feelings. てたまらない emphasizes degree, as in かゆくてたまらない (It’s so itchy I can’t stand it). てしょうがない also shows intensity but leans toward inevitability, as in 暇でしょうがない (I’m unbearably bored).

Both express strong emotions. てならない often implies natural, uncontrollable feelings and sounds formal, as in 心配でならない (I can’t help but worry). てたまらない emphasizes unbearable intensity, often colloquial, as in 会いたくてたまらない (I’m dying to see you).

Both describe situations beyond control, but differ in meaning. てたまらない expresses unbearable feelings or desires, often casually, as in 会いたくてたまらない (I miss you so much I can’t stand it). ないわけにはいかない shows unavoidable obligation due to duty or circumstances, as in 助けないわけにはいかない (I can’t very well not help them).

Both convey extremes but differ in tone. Adj限りだ attaches to adjectives to show feelings at the utmost, often formal, as in 嬉しい限りだ (I’m extremely happy). てたまらない highlights intense emotions or desires that feel unbearable, used more in casual speech, as in 会いたくてたまらない (I miss you so much I can’t bear it).

Both express uncontrollable actions or feelings, but differ in nuance. ずにはいられない is about being compelled to act (lit. 'unable not to act'), e.g. '彼を応援せずにはいられない' ('I can't help but root for him'). てたまらない emphasizes a state or feeling that overwhelms you, e.g. '暑くてたまらない' ('It's unbearably hot') or '会いたくてたまらない' ('I want to see you so much I can't bear it').

Both ことに and てたまらない express emotion, but in different ways. ことに highlights the speaker's emotional response to a situation, usually following an adjective or verb, e.g. 悲しいことに、誰も来なかった 'Sadly, no one came.' てたまらない conveys an overwhelming personal feeling, often physical or emotional, e.g. 会いたくてたまらない 'I want to see you so badly I can't stand it.'

ざるを得ない expresses unavoidable action due to external circumstances, as in 行かざるを得ない (I have no choice but to go). By contrast, てたまらない conveys an intense emotional feeling that is hard to endure, as in 会いたくてたまらない (I can’t help wanting to see you). Both imply compulsion, but one is situational, the other emotional.