I second The Chaser; especially since you liked Two Weeks, I'm sure you'll like Chaser too!
Other dramas that haven't been mentioned yet are Golden Empire (from the same team as The Chaser), Flower Grandpa Investigation Unit for something funnier, Hanzawa Naoki, Kazoku Game, Dae Mul and A Wife's Credentials. The last two have a bit of romance, but other topics are a lot more important.
Edit: Ah sorry, I missed that you only asked for Korean dramas, but the two Japanese ones I mentioned are really good, too^^