T-1000 (Judgment Day)

The T-1000 is a liquid-metal android, whose main goal is to kill John Connor in the past. Unlike the last Terminator, T-1000 can survive most any injury and changes back to it's origional form almost instantly. He disguised himself as a cop in T2.

Story
As the super-computer Skynet became self-conscious, it started mass-producing the terminators, in order to wipe out the humans from the face of earth. A human resistance was leaded by John Connor, who organized the survivors of the Judgement Day to fight the machines. Skynet then sent a terminator to the past to kill Sarah Connor before she gave birth to John. As the first Terminator failed, Skynet took the next step and sent another terminator, the prototype T-1000, to kill John while a child. John managed to capture a Terminator and sent him to the past as well to protect himself in the past.

Personality
Altough the T-1000 is a heartless machine, he shows some traces of cynism and sarcasm.