When Laertes receives word of his father's death, he drops everything in Paris, immediately returns to Denmark, organizes a mob, storms the castle, and bursts into the King's chamber like awesome, ready to deliver some serious hardcore retribution to his father's murderer. And then for an encore, he kills the titular character in the very next act.
Hamlet's killing of Claudius in the final scene.
Hamlet: The point!—envenom'd too! Then, venom, to thy work. (Stabs Claudius)
Hamlet's letter describing his MacGyvering an execution order for Rosencrantz and Guildenstern, and his escape from the ship.
The climax of the first scene of the final act, where Hamlet reveals himself to Laertes at Ophelia's funeral after having secretly returned home to Denmark. One of the greatest He's Back moments in all of literature.
Hamlet: What is he whose grief Bears such an emphasis? Whose phrase of sorrow Conjures the wandering stars, and makes them stand Like wonder-wounded hearers? This is I, Hamlet the Dane!