Any situation where the child's well being is in grave danger (such as running in the street) and your hitting them is the most effective way to prevent this from happening. I would add that even in such situations the parent must be certain that they are not hitting out of anger or frustration.
I'm unsure if you are referring to preventing the child from doing dangerous things in the future, or if you're talking about stopping a child who is in the act of doing something dangerous. Either way, I disagree:
If you are referring to the most effective way to stop a child who is in the act of running into the street or touching the stove, hitting is certainly not the best way to accomplish that. If you are in close enough proximity to hit, then you would be much wiser to grab the kid by the arm and forcibly move them away from the street or stove. That action would save more lives than hitting would, most definitely. If you are not in close enough proximity to grab the child, and the child is about to run into the street or touch the stove, you should scream for them to stop and hope it works.
If you are referring to the most effective way to
prevent the child from running into the street and touching the stove in the future, hitting, again, is a far cry from the most effective method. Depending on the child's age, different methods may be the most effective, but hitting is not even in the discussion in my book.