Regicide is defined by the Webster's Dictionary as "The killing of a king". Webster could not have oversimplified this representation more. The ancient art of king killing has existed in a myriad of different forms; stealthy, barbarian, and honorable regicides have been recorded liberally in both literature and the annals of history. Regicide is an act of enormous weight - it takes an extraordinary stimulus to move a man to commit such an act. In Hamlet and Macbeth, William Shakespeare uses four acts of regicide to bring to light the important motives of the killers, and through the motives showcase the protagonists' tragic flaws.
There are two instances of regicide in both "Hamlet" and "Macbeth". In both stories, ambition and power-lust bring about the first set of regicide. Claudius killed King Hamlet, his brother, because he wants the power of the throne. The two characters, antagonist and victim, are clearly juxtaposed in personality by Shakespeare to create a contrast between the two figures that Prince Hamlet later draws on to motivate his own act of regicide.
Claudius is a political figure. He schemed, lied, and spied on others. Indeed, he killed King Hamlet by pouring poison into the King's ear. This act was a symbol of not only Claudius' scheming nature, but also how Claudius took advantage of others by poisoning their ears and thus making his set of ears more powerful. His ear poisoning also foreshadowed his use of eavesdropping later, as well as the poisoning (killing) of one of Claudius' surrogate ears, Polonius.
King Hamlet's personality is entirely different from Claudius'. Hamlet Sr. was not political. He did not scheme, but in fact dealt with things directly. He was a warrior-king, and deals with problems as if they were an opposing army on the battlefield. Seen...