One of the biggest challenge in developing a terminator grade robot is making a robot know what to expect. A robot caught by surprise/something he hasn`t foreseen poses danger to himself and those around him. There are events that even a human can not predict, like a falling meteorite from the sky, no one can predict that. If a robot fails into a situation that even a man couldn`t have predicted that`s excusable. But a robot that`s acceptable for the society is a robot that is prepared for a given situation like an average human in the same situation would.