What does the end of the chronicle of sin mean?

1. The reversal at the end of "Chronicle of Evil" is that the real Jin Zhenkui surfaced, and teenagers saw their father being beaten and abused, and dared to take poison to poison the violent man.

When he admitted his mistake to the police and was ignored by the police, he left a deep shadow in his little heart, which could not be erased for more than ten years after being adopted. He said that from the moment his father was taken and sentenced to death, he was waiting for these policemen to be retaliated one by one.

Finally, the ending he planned for many years came. He shot himself, because the revenge was over and the meaning of his life was gone. The monitor Cui didn't kill him, he just freed himself.