[boomlinde]

Approach 1 seems quite natural. If I do something—in general—and find that it results in my suffering, I will normally take that into account when I consider doing the same thing again, and possibly avoid it because of it. In this sense I don't think that getting slapped or putting your hand on the stove for the first time are significantly different. You learn the consequences and adapt.

In the case of a bully, though, there may be so much at stake for the bully that it outweighs the suffering associated with getting beaten up or otherwise punished for it. Wishing to e.g. maintain his social status, he may double down instead of reacting in a way that seems appropriate given the obvious consequences. This is where I think approach 2 becomes useful. What is it that the bully thinks is at stake? etc.

Before that, who cares? Kids will be kids and will fight and bicker. That's how they learn what their boundaries and what the consequences of their actions are so that they can grow up to be healthy adults. I think that inflicting pain and suffering as a direct response to injustice may be an excellent way to keep misbehaving adults in check as well, but it seems more likely in adult age that there is an underlying psychological problem that needs to be addressed, perhaps one that could have been addressed during adolescence.