Clearing up the misconception that many of you seems to have
The note that is given by the terrorist group at the end to Park is NOT the same note Young-Mi wrote at the start. I'm baffled to how some of you could possibly think this as Young Mi didn't even know of Park at the start of the movie.
The note at the start orders death sentence to a completely different guy. This person (not shown in the course of the film) was sentenced to death for wrongly involving the police to kill 4 of his employees during a Worker's strike.
The note that is given to Park at the end is also a death sentence but it reads something like: The defendant Park is proven guilty of murdering the Anarchist member Cha Young-Mi, it is decided unanimously by the panel that the death sentence is carried out to the defendant Park in the name of justice.
Source: I'm Korean.