中々(なかなか)～ないNot really, Hardly, Not easily or readily, By no means, Far from

なかなか means 'quite' or 'fairly' when used with positive expressions, e.g. なかなか面白い映画だった ('It was quite an interesting movie.') In contrast, なかなか～ない expresses difficulty or delay, meaning 'not easily' or 'hardly', e.g. 仕事がなかなか終わらない ('The work just won't end.')

Both negate expectations, but in different ways. 別に〜ない downplays something as not particularly important, e.g. 別に怒ってないよ ('I'm not especially mad.') なかなか〜ない indicates that something doesn't happen easily, e.g. なかなか怒らない人だね ('He's not someone who gets angry easily.')

Both express rarity or lack of frequency, but with different focus. 全く〜ない means something happens infrequently, e.g. 全く外食しない ('I hardly ever eat out.') なかなか〜ない suggests it doesn't happen easily or readily, often due to circumstances, e.g. 忙しくてなかなか外食できない ('I can't easily eat out because I'm so busy.')

なかなか～ない and あまり～ない both express negation, but with different nuance. なかなか～ない implies difficulty or delay despite effort, e.g. なかなか話せない ('I can't speak easily.', implying difficulty despite effort). あまり～ない simply indicates a lower degree, e.g. あまり話せない ('I can't speak very much/well.').

なかなか～ない expresses that something is not easily done, often implying difficulty or repeated effort. For example, なかなかうまく話せない ('I just can't speak well.') has the nuance that the speaker is trying but not succeeding. In contrast, すこしも～ない means 'not even a little.' 少しも話せない means 'I can't speak at all.', focusing on the absence of ability without any implication of effort or struggle.

めったに〜ない and なかなか〜ない both express rarity, but with different nuance. めったに〜ない means something rarely happens and carries a neutral or negative tone. なかなか〜ない, while also indicating rarity, emphasizes difficulty or persistence, often despite effort. It suggests that the situation is hard to bring about, rather than simply uncommon.