今更(いまさら)

今更(いまさら)ダイエットを始(はじ)めても無駄(むだ)だ。

Starting a diet now, after such a long time, is pointless. {now (after such a long time), at this late hour (i.e. it is too late for something), afresh, anew, again}

もう彼(かれ)を十分(じゅうぶん)注意(ちゅうい)したので今更(いまさら)注意(ちゅうい)はしません。

I have already warned him enough, so I won't warn him again, especially not now after such a long time. {now (after such a long time), at this late hour (i.e. it is too late for something), afresh, anew, again}

部長(ぶちょう)：「計画(けいかく)を変更(へんこう)したい？今更(いまさら)何(なに)を言(い)っているんだ！」

Manager: "You want to change the plan? What are you saying at this late hour!" {now (after such a long time), at this late hour (i.e. it is too late for something), afresh, anew, again}

結婚(けっこん)三(さん)年目(ねんめ)を迎(むか)えた節目(ふしめ)に、今更(いまさら)ながら結婚(けっこん)指輪(ゆびわ)を買(か)いました。

On the milestone of our third wedding anniversary, we bought a wedding ring, albeit now after such a long time. {now (after such a long time), at this late hour (i.e. it is too late for something), afresh, anew, again}

友達(ともだち)：「何(なに)？ごめんなさい？今更(いまさら)謝(あやま)ってももう遅(おそ)いよ。僕(ぼく)たちは絶交(ぜっこう)したんだ。」

Friend: "What? Sorry? It's too late to apologize now, after such a long time. We've ended our friendship." {now (after such a long time), at this late hour (i.e. it is too late for something), afresh, anew, again}