Revenge is a strong emotion wanting to get retaliation for a wrong a person believes has been done to him/her. The saying goes "revenge is sweet", however, it is a destructive, uncontrolled emotion that will eventually cause emotional, physical and psychological harm to all those involved.
Let me know how this works. After you state this, you have to find viable arguments to support it. Your final paragraph should restate your thesis. The use of Hamlet will work as a literary example. Hamlet was obsessed with revenge but it only led to his death, and that of many others, in the end.