こそ

彼は年こそ若いが十分その仕事をやっていける。

Young as he is, he is equal to the task.

辛抱こそ大事なんだ。

It's patience that counts.

こだわりはお客に伝わってこそ意味をなす。

Care over the particulars only has meaning once it gets across to customers.

君のためを思えばこそこう言ってるんだ。

It is precisely because I have your best interests at heart that I am saying this.