My MIL has threatened my girls, which I really don't like, but has never smacked them. I really don't think she ever would.
My mum has smacked my DD's & neice. DD1 I don't remember (not even sure if she has to tell the truth), but DD2 & my neice ran off & ran across a road. I was pushing a pram & mum ran after them when they ignored us & kept running.
Thats the only time I can remember her doing it & that was purely for their safety & to hope they never do that again.