The mask of pain on Walt's face when Hank is killed and that last good part of him just dies. The way he coldly sentences Jesse to die (or unwillingly to end as the Nazi's meth kitchen slave) and on top tells him, that he let Jane die.
And then the scene where he rolls a round his barrel, the song about his one true love playing in the background. And finally his showdown with Skyler. This was also textbook Shakespeare tragedy. She really is his Lady Macbeth.
I'm also kind of happy about how completly obviously evil Walt was when he threw all that blame and insults at Skyler to whitewash her for the police. The Skyler hate is what keeps me from the BB fandom at large (fortunately here on LJ I have never witnessed it) and this was basically their talk thrown back in their faces as "wanna sound like a crazy abusive asshole? here is your script.")
I really did not think my hear could be broken so many times in one hour and there are still two more episodes to come. How can this show be so damned evil and excellent?