1. Taking everything personally

2. Obsessing about negative thoughts

3. Treating yourself like a victim

4. Cruelty - lacking in empathy or putting yourself in others shoes

5. Excessive reactivity

6. Needing constant validation

In my thinking, lack of empathy spans them all. 

I do not think there are too many people, who do this purposefully. This kind of behavior usually comes out under pressure, stress and confusion. Empathy and the culture of open communication is very important.

Most people have good intentions, even if their behavior is bad. 

It's hard to recognize bad behavior in oneself -- but it's also hard to listen to feedback after behaving badly!

Agreed. First step is awareness and better to read and find in yourself, than to listen to feedback from the behavior itself. Even the best of people have shown these behaviors at some point in their lives. 

I know I've been guilty myself in the past.

It's still hard to listen to feedback when you realize that your behavior has been bad.

Me too and I would be pressed to find someone who hasn't.  It's hard whether you are aware or not. I found during these times it's important to be around people who know where you're intentions lie and only give you feedback when asked. Then figure it out what is making you unhappy. 

Yeah, the key is to find people you trust. Easier said than done!