〜こそ

今度こそ成功させます。

Kondo koso seikō sasemasu.

This time I will make it work.

こそ singles the word out for emphasis, often with resolve

こちらこそよろしくお願いします。

Kochira koso yoroshiku onegai shimasu.

The pleasure is mine.

The set return in a greeting, handing the courtesy back

失敗したからこそ、学べました。

Shippai shita kara koso, manabemashita.

It is precisely because I failed that I learned.

After から it insists that is the very reason