2. The T-1000 Terminator 2: Judgement Day
What Its Deal Is: The Terminator series was lamenting the future of robotics way before the Matrix tried its hand. In T2: Judgement say, the sentient machines continue their mission of sending Terminators back in time to assassinate John Connor before he can become Camerons version of The One. The T-1000 (Robert Patrick) is more than just a robot; hes an amorphous shapeshifting blob of liquid metal, who cant be killed, or even damaged with conventional weapons. Oh, and he can assume the identity of anyone he sees too, meaning that if theres ever someone on screen that youre not quite sure of, its probably brown trousers time.
Why Itd Be Unstoppable: Hes stopped in Terminator 2 when hes dumped unceremoniously into a vat of molten metal; he cant reconstitute and therefore cant pose much of a threat to anyone. But, John Connor was lucky. Had it not been for the convenient location of that steel mill, youd never have managed to get the T-1000 anywhere near a pool of molten metal, let alone to take a bath in it. In reality, you have to imagine that a robot from the future would probably be smarter than that. And given the fact that the T-1000 is clearly superior to the T-800, this defeat is probably about as likely as an original Xbox out-powering a 360 for graphics - its just not going to happen. The best John Connor, and humanity as a whole, could really hope for is a quick, painless death.