Good cop ; Bad cop

Does a cop become abusive after being a cop for some time or do they become cops because they need the power to be abusive? It might be a question as complicated as the question that asks what came first the chicken or the egg. What a lot of people tend to forget is that cops are just people too, they get mad and frustrated just like everyone else. Imagine if in your line of work you have to “serve & protect” people that see you as the enemy. If 8 out of 10 people you talk to flat out lie to you even dough both know you are right. If you arrested a guilty person then later on you arrest that same person for the same crime that you had already caught them for. How much can a person that wants to make a difference take before they just end up giving up on the situation? On the other hand, some people become cops especially for the power they have over people. In the movie Righteous Kill, there is a line that says it all “Some people respect a gun, everyone respects the badge”. When you are the person that is supposed to protect but instead you are the abuser, who does the person being abused go to? Who is the person taking the report going to believe a fellow cop or some person that is most likely lying or stretching the truth to them? Knowing that as a cop one can get away with almost anything is intoxicating. Who is going to stop you when you and your friends are the law? Who is going to believe that a cop planted evidence against them?