'Deadliest Warrior' shows the flip side of that. In the Celt vs Persian Immortal episode; the celt (admittably a big chap) hit a trauma torso with a short stick and removed his brain! The Jesse James pistol whip was also a deadly blow.
And just as you can beat the odds and survive what should be deadly impact, the reverse can happen. There's been cases where someone got punched in the face once and died of it. If it's enough to knock you down (which might be very little depending on thier balance) it's enough to make a head hit a pavement.
Any blow to the head is a very serious matter. Don't inflict it unless you are willing to go to prison.
qjs