Bullying can be defined many ways, as it’s a form of abuse be it towards other children, spouses and, of course, elders.
It’s not that no one is prone to bullying; as Jordan Peterson has said, the most aggressive people on the planet are two-year-olds who bite, hit, kick, ignore personal boundaries, throw their spoon and dish to the floor, etc., it’s that mere aggressiveness only hardens into a pattern of bullying when the child learns that there are no consequences to it. Indulgent or neglectful parents, or parents who themselves are abusive, can teach the child that bullying is a valid way to be; or parents can nip it in the bud.
Bullies can be found everywhere in history, but not all societies produce the same number of them. I read somewhere that it used to be good sport to trip blind people, etc., in the Middle Ages when blindness was viewed as a curse by God. Now who would think to do such a thing?
Unfortunately now, so to speak, a “blind eye” has often been cast on potential bullying problems for the simple reason of a familiar chant from mostly mothers, from my readings and experiences that their “little Johnny would never do such a thing,” that “he is a good boy!” I still hold to my statement that bullies are not born being bullies, but learn that their aggressive impulses can be embraced, turning them into a chronic bully, and some sooner than others for various reasons.