GLaDOS is the main villain from the surprisingly awesome Portal video game from Valve, and soon to be featured in Portal 2.
GLaDOS was built by engineers at Aperture Science to oversee the testing chambers of their experimental new Portal technology. GLaDOS runs the facility which consists up multiple puzzles designed to be solved using Portals, with the promise of cake as a reward for their cooperation. Then she flooded the lab with a neurotoxin which killed all of the employees and has the test subjects end their experiments by being burned alive. If they survive, GLaDOS makes fun of them. In short, GLaDOS is a robot Joker, but with a soft friendly voice.
Hell, according to Portal's backstory, previous test subjects were so depressed in the isolation of the chambers that they fell in love with the Companion Cube, a little box that GLaDOS provides you to place on big buttons that make doors open. Realizing this, she has you incinerate the Companion Cube, and then insults you for murdering it. That sort of evil makes Bowser seem like Mother Teresa, except in dragon/turtle form.
Here are some choice excerpts from GLaDOS' surprisingly diverse pool of pitch-black insults:
"I was going to throw you a party and your friend Companion Cube was invited. But oh yeah you murdered him. None of your other friends could make it because you don't have any other friends."
"They are starting to cut your your cake. I told them to wait but they started cutting it and they didn't even save you a piece."
"You were adopted, so there's that."
"The penalty for failing to complete the tasks in the correct fashion is a low-mark on your test record, followed by death."
GLaDOS hates you so much that even after she is defeated in the climactic boss fight, she brags that she is still alive in song form. She is literally so happy to keep tormenting you that she has to burst out in song. And we thought Sex and the City 2 painted a negative portrayal of women; Portal has got to be one of the most delightfully misogynistic games around.