There are two kinds of mean people in the world

The first kind, is the person who is mean because of experience.
We don't often get to choose what happens to us. I literally believe that we are given a life and we have to come to terms with how that is. You can try to change it but whether that is successful or not isn't even up to you. All you can do is give it a go. Some people cop the bad stuff again and again for no apparent reason at all. No wonder they turn out to be the way they are. They happened to step right into all the wrong situations at the right time completely unaware. We should remember to not take these people to heart too often because their coldness and bitterness is really a reaction to the world and not to us as individuals. They did not willingly choose the paths they took which lead them to where they are now. It's by sheer misfortune that we are born into the people that we are which is the saddest fact of all. We are given a life and we must spend our entire lives coming to terms with what we've been dealt.

The second kind, is the person who is mean because they get enjoyment and a power trip out of making other people feel bad or scared of them.
This person can be born out the first category but usually I feel like they are a category within themselves. People get power trips from belittling others. I think this is the cheapest form of power seeking as it directly aims at making someone else feel like shit. The most powerful people I know bring people up and make them feel positive. It's a different story if you genuinely dislike somebody. That's fine, but to go out of your way to make them feel like shit to their face is another matter. The more you seek to destroy or to make someone else feel bad, the more people who'll steer clear from you. I feel like often people get confused with what is direct vitriol or simply being upfront. It's hard to differentiate sometimes because what feels mean or hurtful is simply ' bad ' as we like to generalize. But people who seek power from belittling others have your wounded self esteem as their trophy. People who are being upfront state the truth without desiring any form of sadness from you. In other words, it's not even about you. It's just about being honest.