“After the event” in Chinese is 事后 (shìhòu).
但是，当然啦，事后诸葛亮总是好当。
But, of course, hindsight is 20-20.
Example sentence from Tatoeba (CC BY 2.0).
Not to be confused with: 侍候 (shìhòu, to serve) · 时候 (shíhou, time)