Claudius should have been rightly accused and convicted at the legislative level—through the court. Hamlet had no proof of Claudius’s guilt except an indictment of a spirit. At first, he was too conscientious about committing cold-blooded murder. Once he obtained evidence, he was sure of Claudius’ guilt, but Hamlet could do nothing except murdering him. Claudius was dangerous, manipulative, and, as a horrible king, above the law. Killing him was not only revenge but salvation for Denmark.
Detailed answer:
In the given era, slogans like “eye for an eye, death for death” were still relevant. When the ghost of Hamlet’s father claimed that he had been poisoned, the ask for revenge was nothing out of the ordinary. Yet there was no guarantee that the spirit was not a devil or just symbolic grief from losing his father. And that’s only one side of the story. The main reason why Hamlet is wrong in his plotting against Claudius is that he is not able to make up his mind. He overthinks and analyzes too many possible approaches to any question.
Indeed, what Hamlet would become if he fell upon a defenseless enemy? Or even at that moment when he completely surrendered to sincere repentance? A killer and nothing more. And who would Claudius become? His sacrifice, a helpless and pathetic victim. Hamlet does not want to allow such a turn of events.
His actions tend to be impulsive, but in this case, he carefully weighed and thought over the murder. To kill Claudius at once means to save his soul and destroy his own. Hamlet does not murder him for obvious reasons. He needs an absolute victory over the enemy, without misinterpretation.
Hamlet’s trouble was that Denmark was not ripe for a real uprising. It was a prison with many dungeons, with no legal power over the monarch. In particular, such manipulative king like Claudius, whom people viewed as the country’s savior. In such circumstances, each prisoner had to rely only on themselves. The people, as Claudius admits, love the prince but do not rise. Hamlet rises but does not think about the people.