We cannot write essays for you on eNotes, but perhaps we can help you think about what to write and how to write it.
First, you should decide whether you want violence to be a cause or an effect (or both) in your essay. Next, you will need to think about what causes and/or effects of violence you want to talk about. It may be useful to reverse the steps in this process. You might want to think about what the causes and effects of violence are. Then, if you cannot (for example) think of enough effects of violence, you can make violence be the effect and then explore its causes.
For some causes of violence, consider the following. Violence might be caused by poor parenting. It might be caused by excessive exposure to violence in TV shows and video games. It might be caused by the culture of the people who commit violent acts. It might be caused by frustration on the part of people who cannot get ahead in society. All of these are potential causes of violence.
For some effects of violence, consider the following. It might cause a lack of trust among members of a society. It might cause more racism if people of one race feel that the other race is more likely to be violent. It might cause people in violent neighborhoods to have lower life chances if they are, for example, afraid to go to school.
Now, start to write your essay. Pick a few causes and/or effects and explain their links to violence as clearly as you can.