I'd like to offer an easy way to discipline a spoiled child without using ANY physical force, and it is 10x more effective in my experience.
Although I've never had children, I did social work as my first job out of college with children from broken homes, and they would often be unruly. Using the following technique, which I learned from my family (who also never hit me, although I got slapped in my face in my teens once), you can control any child under the age of 12 effortlessly:
Tickle Torture.
Any young child who is excessively crying for something, or being spoiled, or whining, or hitting his siblings, or doing something you don't like - you just start tickling them relentlessly until they stop.
I personally like to take my pinky finger and dig it right into the pressure points of a young child: around the collar bone, the sides of the ribs, under the armpits, etc.
They can be crying because you won't give them their favorite candy, and immediately switch to laughing hysterically and begging you to stop. I usually say something like,
"If you don't stop doing X, I'm going to have to tickle you..." And when it starts I say "Tickle tickle tickle tickle tickle tickle tickle (etc)" in a high pitched voice until they are rolling on the ground screaming for mercy while dying of laughter as tears come out of their eyes. My father would do the same thing to me if I was spoiled.
For children under 5, it has worked for me 100% of the time! And the best part is, you won't feel guilty at all. Your wife or other women around you will be laughing too, because no harm is being done to the child. You just keep tickling the child until the child agrees to stop doing whatever it is you want them to stop doing.
It may sound ridiculous, but once you try it you'll never go back to any other form of discipline for young children.