Director: Chan-Wook Park
This Korean film was a huge success internationally and has developed a massive cult following, so if you have yet to see it, I suggest you get right on it. When the protagonist is imprisoned for 15 years for seemingly no reason, upon release he is given 5 days to find out who his kidnapper is and why he was imprisoned. ‘Oldboy’ feature excellent action scenes, a scene where a man eats a live squid(!) and one of the most disturbing endings you will have likely seen.
Also recommended are ‘Sympathy for Mr. Vengeance’ and ‘Lady Vengeance’ which together form a loose trilogy, connected by their common theme of revenge.