Laertes had these worlds to say, "O treble woe/ Fall ten times treble on that cursed head/ Whose wicked deed thy most ingenious sense/ Deprived thee of.?(5.1, 246-248) Laertes blamed Hamlet for the deaths of Polonius and Ophelia and challenged Hamlet to a fencing dual which would be rigged by Claudius and Laertes...
The same soliloquy makes it clear that Hamlet finds neither of the reasons he considers for his delay convincing.
That the cause might be ‘some craven scruple / Of thinking too precisely on th’ event’ (4.4.40–41), as a result of which action becomes impossible, might seem plausible.
Deep into Act 4 he finds himself shamed yet again for dragging his heels, this time by the sight of Fortinbras’s army marching headlong to their doom, merely ‘to gain a little patch of ground / That hath in it no profit but the name’ (4.4.18–19).
And he voices his bewilderment at his inexplicable inertia once more in his last great soliloquy: ‘I do not know / Why yet I live to say “This thing’s to do”, / Sith I have cause, and will, and strength, and means / To do’t’ (4.4.43–46).
But when it came to killing Polonius, and sending Rosencrantz and Guildenstern to their deaths, after finding his own letter ordering his death, that was easy and he acted on impulse. Was Hamlet enjoying acting insane and subconsciously did not want it to end therefore not really wanting to kill the king?
When Hamlet was in the graveyard and met the grave digger who had no sympathy for the dead which offended Hamlet, I agreed with Hamlet.
The retribution he happens to exact is exacted too late, moreover, to prevent all the deaths that need not have occurred, if only he had killed Claudius sooner.
As a direct or indirect result of his procrastination, Hamlet slays Polonius instead of Claudius; Ophelia goes mad after her father’s murder and drowns; Rosencrantz and Guildenstern are dispatched by Hamlet to their deaths; and in the play’s climactic duel Hamlet’s mother drinks from the lethal cup intended for her son, who is fatally wounded by Laertes in revenge for the deaths of his father and sister.
The man who started it all is worried about being found out.
In order to keep his actions covered up he Thus proving that to achieve their revenge they had to die and did not get the chance to enjoy any satisfaction they may have had.