What is one way to stop or prevent bullying?
One way to prevent bullying is to scrutinize the powerful (phsyically and mentally) and the popular and prevent them from taking actions to increase their own power. Power corrupts people and turns disagreement into violence. Without power, there can be no bullying, just animosity.
If you undermine those with power, those without power won't feel compelled to join in on their side, and bullying will stop.