I watched the First episode the day it was released. The violent bullying triggered me and I couldn't watch past it. Took a break of 15-16 days and then watched from the second episode. I don't think I would ever watch the first episode again.

But kudos to the actors especially Shin ye sun who played teenage Ji-yeon for making it so realistic that I literally hated that character.
This is my first drama of Song Hye-kyo and she nailed it. Its a slow burn revenge and the writing and execution is perfect.
Waiting for the second part (Although in my opinion there was no requirement of releasing in installation).