Also, people have survived jaw-dropping (sorry) injuries and accidents that involve being impaled through the head/brain. The pic linked to in the OP could (should) be a deadly blow, obviously, but depending on what was actually injured in the brain, it’s possible the blade only severed the two hemispheres of the brain, which wouldn’t necessarily result in immediate death, and if survived, would result in some rather peculiar behavior and perception from the victim but could lead an otherwise decent life.
A coconut from the grocery store - not the whole husk ones you find in the tropics - is a suitable stand in for the human skull. So, yes with bullets, swords, or hammers you can devastate a skull.