I'm not sure. Bullying, offline and online, is rarely done to random people you don't have any connection to and without other people. It either ties into offline, i.e. they're bullying someone they know, or it's an online community thing where some people from some community have fun together bullying someone they might not know.

My point is: in both cases it's not "I'm miserable and unhappy", it's either a community-building thing, or it's a social status thing. If you're bullying someone in school, that's a power move to assert status. They're not unhappy, they're just trying to get ahead; under different circumstances, they'd just mug people to take their money. Now they bully them to get more status.