A day may come when I may be able to do something for you to repay your kindness.

也许有一天我能为你做些事情来报答你的仁慈。

youdao

I told him I'd repay his kindness to me and I will-i regard it as a debt of honour.

我告诉他，我会报答他对我的仁慈而且我一定会的——我把那视作信用借款。

youdao

I owe them kindness that I have a lifetime to repay a never-ending.

我欠他们的恩情，是我一辈子也偿还不完的。

youdao

The second, somewhat at odds with the first, was an instinct for reciprocity a tendency to repay kindness with kindness and betrayal with revenge, even when rational calculation might seem to advise against it.

ECONOMIST: Economics focus