あれが最後だったのかって英語でなんて言うの？

この場合、次のような言い方ができますよ。 ーI guess that was the last time I'll ever see him. 「あれが彼に会う最後だったんだな」 ーI took it for granted that I would see him again, but it looks like that was our last meeting ever. 「また彼に会えると当然のように思ってたけど、あれが彼に会う最後だったのか」 ご参考まで！