With that caveat, on access-controlled highways (motorways), you’re not allowed to walk, so any pedestrian would be in the wrong for being there. That said, even there a driver would be at fault for colliding with a human (policeman, fireman, people after a car accident, and other people who might have a very good reason to be there) regardless of what that human was doing. It’s not that different from crashing into a stopped car or any other kind of obstacle. Similarly, a driver is at fault for hitting an animal.
In non-access controlled highways, the driver would be at fault if their car collided with anything, be it another car, a human, or an animal. How legal it is for a pedestrian to cross in this case depends on local laws.
So in any case, yes, the driver is responsible, although that responsibility could be shared in some cases. If the accident results from deliberate action on the part of the pedestrian, there probably would not be any consequences for the driver in any lawsuit (unless the driver was also reckless or drunk), but for insurance purposes it does not matter.