Correct

悔不当初

/ huǐ bùdàng chū / 
Strokes

Definition

to regret one's past deeds (idiom)

Example

Definition

regret having done sth

1
Zǎozhījīnrì
早知今日
  
,
huǐbùdàngchū
悔不当初
  
。

If I'd known then what was going to happen, I wouldn't have done as I did.