in retrospect
US /ɪn ˈrɛtrəˌspɛkt/
UK /ɪn ˈrɛtrəˌspɛkt/

1.
when thinking about the past, especially with the advantage of knowing how things turned out
:
•
In retrospect, I should have taken that job offer.
•
The decision seemed right at the time, but in retrospect, it was a mistake.