Thanks a lot, Ack. Believe it or not, I started to post replies about Oldboy three different times and each time was unable to complete it (twice due to time constraints, and once due to a power fluctuation that killed my internet access for a couple of hours). Ultimately, you wrote a much more clear and concise post than I would have.Ack wrote:
You missed a couple of things about the plot I feel should be pointed out, because it's influenced how you feel about a specific character.
Said "jackass" could accept responsibility for his actions: he had no trouble with his incestuous relationship with his sister. But the sister has trouble dealing with it, and during one of their encounters, the main character witnesses them in the act and tells. The sister, unable to handle the discovery, commits suicide. The jackass then wants revenge against the first character for catching them, which ultimately led to his sister's death, so he plans an elaborate revenge in which he torments the man and then arranges things so the man has an incestuous relationship with his daughter. Finally, he kills himself, depriving the other man of his retaliatory revenge.
Ultimately the film is about one man attempting to get revenge on another man who's currently getting revenge, cycling their spite for each other with each new event. And that's ultimately what the Revenge Trilogy is about: how little revenge accomplishes.
Though I would argue that Lady Vengeance has the most positive ending out of the three. And the most satisfying.
I agree that Lady Vengeance is the most satisfying of the three in terms of seeing revenge completed. It's hard to say that things end well for her, though. At the end she seems to regret what she did pretty strongly.

