This is hard, because my favourite movie is "The Wall," but from the standpoint of writing, direction, and overall quality, the "best" movie I've ever seen by those standards is "The Kind Hearted Geum-Ja" (Also known as "Lady Vengeance." The previous is apparently the direct Korean translation.) I know many people consider OldBoy to be the best of the Vengeance trilogy, but as much as I love it, Lady Vengeance did more for me. It's one of the few movies that really moved me. It's genuinely disturbing in some aspects, and it's not for the squeamish (The villain is easily the most detestable I've ever seen in a film, and honestly he's made creepier by the fact that he's easily the most realistic.) in both the violence and sex department, but as far as a dramatic story with brilliant characters, incredible visuals, a great score, and a near perfect plot, it's amazing. It's also one of the few movies to make me cry more than once. I can think of three scenes that actually moved me, and the ending always gives me chills. It also gets bonus points for having a double barreled revolver. That's just awesome right there.