Both Hamlet and Laertes are driven by a desire for vengeance. Hamlet, of course, has a mandate from his father's ghost to avenge his death. Hamlet's quest for revenge represents the main thrust of the plot, as he vacillates, hesitates, and reflects on the evil he witnesses around him. He even passes on one chance to kill his uncle, in a memorable scene in which he encounters him praying. By the middle of the fourth act, however, is determined to gain revenge. Reflecting on the courage shown by young Fortinbras and his army, who are marching through Denmark to fight a battle, he swears:
O, from this time forth,
My thoughts be bloody, or be nothing worth!
Laertes, on the other hand, is driven to avenge his father's death, as well as that of Ophelia. He blames Hamlet for both, and swears to gain revenge:
And so have I a noble father lost;
A sister driven into desperate terms,
Whose worth, if praises may go back again,
Stood challenger on mount of all the age
For her perfections. But my revenge will come.
When Claudius and Laertes discover that Hamlet has returned from his trip to England (where, of course, Claudius hoped to have him killed) the King enlists a very willing Laertes in a plot to murder Hamlet. Laertes insists that he be allowed to kill Hamlet himself, even to "cut his throat i' the church," and Claudius agrees. In the climactic final scene, of course, both Hamlet and Laertes gain their revenge, though it comes at the cost of their young lives.