Is Hamlet a vindictive murderer or a moral idealist?

Probably the only character in Shakespeare's Hamlet who would call the prince a vindictive murderer would be his intended "victim," his uncle Claudius.  Evidence of Hamlet's moral idealism abounds in every act.  

In Act 1, Hamlet clearly reveals that he dreads his filial obligation to commit revenge upon his uncle for murdering his father.  Although Hamlet tells his father’s ghost that he will do it out of love, as soon as the ghost disappears he says, "Oh cursed spite / That ever I was born to set it right."  Hamlet, like most citizens of Denmark in the late middle ages, is Christian, and fears for his everlasting soul.

As further evidence, rather than rushing to commit revenge, in Act 2 Hamlet decides to gather proof that his uncle Claudius truly killed the late king: "The play's the thing / Wherein I'll catch the conscience of the king."  Hamlet also covers his evidence-gathering with a crazy plan to act, well, crazy.  This is more likely to get him thrown in the dungeon than cover his tracks.  Perhaps the prince would rather be imprisoned by bars than by the obligation to damn his own soul to Hell?

With Act 3 comes Hamlet's famous "To be..." soliloquy, in which he longs to commit suicide to escape the "whips and scorns of time," but determines not to because of his fear of the afterlife.  Not quite the private thoughts we would expect of a vindictive murderer, are they? Act 3 also provides his only real opportunity to kill King Claudius and get away with it.  Instead, Hamlet again talks himself out of it, based on the moral belief that he will send his father's murderer to heaven if he kills the man at prayer.  Although Hamlet does kill Polonius, mistaking him for Claudius, most critics will argue that by this point Hamlet’s feigned insanity has so affected him that he acts in a fit of rage.

In Act 4, Hamlet actually gives Claudius warning that he is returning to the kingdom.  A murderer would have sneaked in to commit the revenge, right? Yet a turning point in Hamlet's view of this vengeance comes when he reveals to his friend Horatio that he believes it would be morally wrong to let Claudius live to continue destroying the whole kingdom. Ultimately in Act 5, Hamlet does complete his promise to his father, but only after the entire royal court has witnessed Claudius' murderous nature.  In fact, the weapons Hamlet uses are ironically "provided" for him by the only truly vindictive murderer, King Claudius.