It's the first dark!Bruce fic I've seen so far, and any others will have a hard time measuring up. It is perfection.
Author's summary, long version:
Something happens that makes Bruce angry. So angry that he doesn't hulk out, but stays calm and proceeds to do something incredibly intelligent, precise, and shit-your-pants-scary.
See, the real person to be afraid of isn't the rampaging Hulk but the super-genius who knows how to control gamma radiation and has learned exactly where the most vulnerable parts in the body are and how long someone can stay alive under intense pain. He knows how to break a person mentally, how to prey upon people's fears and out-psyche them. He also knows that there is no stopping himself once someone close to him has been hurt.