In my mind, the primary theme of Hamlet is revenge and betrayal. To me it appears that, throughout the whole play, someone is always trying to get back at someone or is using someone for their own benefit. This theme has always been a common one among playwrights and even modern screenplay writers because it can be very easy to create a very complicated work based on the theme of revenge.
Throughout Hamlet there are different examples of people succumb with the need for revenge. The most obvious example is Hamlet. Hamlet is on a quest to revenge his father's murder. This becomes clear right from Act 1, Scene 5 when Hamlet first realizes that his father's death was not accidental but that his father was actually murdered.
The lines "Adieu, adieu! Remember me." (line 92, Act 1, Scene 5) shows that this is the ghost's intent in coming back to speak with Hamlet. Although he does not say the words "revenge", or kill, he indirectly and subtlety leads Hamlet to believe that he is to avenge his fathers death. When Hamlet repeats the phrase "Adieu, adieu! Remember me!" these words show that Hamlet will not ever forget his fathers plea to him and every time that he sees King Claudius he will see a murderer.
But my question would be, would Hamlet be expected to seek revenge for his father's death? Now that Hamlet has this information is he now obligated to kill King Claudius? I feel that the only way to possibly know the answers to these questions is to be in the situation. I don't think that the rage that Hamlet would feel is possible to feel unless confronted with a similar situation. If my father was murdered I would obviously be very angry and very upset but would I have the rage to kill someone thinking I was right in doing so? I don't know, and I don't think that I could know unless I was faced with that situation.
An example of betrayal rather that revenge would be the fact that Queen Gertrude was very recently widowed and has re-married within such a short time period.