Psychological Projections...

Laertes:

Laertes represents action.  While Hamlet delays action though introspection and intellectualisation, Laertes seems to have an "act now, think later" policy.  Where Hamlet spends the entire play planning to avenge his father’s death, Laertes goes after the king immediately upon his arrival (4.5), and has no reservations about murdering Hamlet the first chance he can get – presumably without any prompting from the supernatural realm.

When Hamlet learns of his father’s murder (1.4), Laertes has already left Denmark, so (if we are viewing Laertes as a representation of Hamlet’s impulse to act) Hamlet’s seeming inability to take action is inevitable.  Laertes does not then return until prompted to do so by Hamlet’s (accidental) slaying of Laertes’ father.  Interestingly, Hamlet’s first two intentional murders, of Rozencrantz and Guildenstern, approximately coincide with Laertes' return.  The final confrontation between Hamlet and Laertes occurs in the final scene of the play.  Hamlet is physically reunited with his active self, and the resulting action leads to the deaths of himself, his mother, Laertes and Claudius.