1. Callousness
Callousness is a quality that means that someone lacks concern or empathy for other people. For example, they would be happy to steal, lie, or cheat without feeling at all bad, or worrying about how this would affect other people. We can see how this would be antagonistic, as it would definitely leave the person on the receiving end feeling stressed out and frustrated.
2. Grandiosity
This is the personality trait of thinking very highly (or too highly) of yourself. It's the impression that someone thinks that they are better than everyone else, and therefore rules don't apply to them. This trait has links to narcissists, who have an unhealthy amount of admiration for themselves. In this case, however, antagonistic people would annoy others by thinking that since they are above them, they can do whatever they want.
3. Aggressiveness
We've all encountered aggressive people before. These people are hostile and rude, and sometimes even violent. Aggressiveness can sometimes manifest physically, but it can also come through in a tone of speaking or the way an action is performed. Unfortunately, antagonistic people may be aggressive or imply aggression which is where a lot of the hostility comes from.
4. Suspiciousness
Antagonistic or difficult people may feel a strong distrust or unease around other people. This suspicion makes them difficult, and when one person is feeling like this it can quickly become mutual. It is hard to feel relaxed and comfortable with someone if you can sense they have a strong distrust of you. With this negative emotion already present, it's hard for the relationship to be uncomplicated.
5. Manipulation
Manipulation means that the antagonist would either attempt to, or has succeeded in, using or exploiting others to benefit themselves. For example, telling them that doing a certain thing would be great for their own good, when in fact it would just be good for the manipulative antagonist. Sometimes ways of manipulation can be so clever they're hard to catch, but anyone who acts in this way is definitely an antagonist or someone you would prefer to stay away from.
6. Domineering
The domineering personality trait means that the person wants to be in control of others. They want to be in charge of how the whole situation is controlled, and they are ready to fight in order to keep this power. This is is egotistical behavior that doesn't leave room for others' desires, needs, or opinions to be taken into account. This is obviously an antagonistic trait, as it is hard to stay calm and talk sense to someone who believes they are more important or powerful than you.
7. Risk-Taking
Lastly, a personality trait that makes up antagonistic people is risk-taking, but not in a good way. Of course, sometimes we all need to take risks. But these should only be taken with proper consideration, and not at the expense of others. Antagonistic people would be looking for ways to take risks in order to get thrills, which are perhaps irresponsible and reckless and puts others in danger as a result. This is unfair to those around them and obviously makes them very difficult people to be around.