It is well known that Laertes is a hot-headed youth. ‘Save yourself, my lord,’ exclaims a messenger (IV, v, 96), when Laertes storms into the castle followed by his follows. Although he has right reason to be infuriated, would it not make more sense to be grieved by the death of your father than to jump to false conclusions? Perhaps his anger is a show of strength, as certainly that is why the people follow him. He is strong and reliable, and perhaps very charismatic. ‘The rabble call him lord…they cry ‘Choose we! Laertes shall be king (IV, v, 104-106)!’ They are loyal to him as he asks ‘give me leave (IV, v, 112)’; there is no rebuttal, simply ‘we will, we will (IV, V, 113)!’
Laertes appears to be a man of action (has he been placed to mock Hamlet and his lack of thereof?), storming into the castle in Act IV, v, and the duel with Hamlet in Act V, ii, should be proof enough of this. He is quick to decide ‘to cut his throat i' th' church (IV, vii, 128)!’ and the terrifying thing is, he seems quite capable to carry through with the plan. He does not seem like a nice guy.
Also note that Laertes does not seem to be an extremely intelligent character. In Act IV, scene v, he has no proof but instantly believes it is the king who killed his father. The king says it was not him who killed Polonius, but does Laertes question the truth in his words? He does not. We know that it was Hamlet who dirtied his hands with the crime, but Laertes was so convinced that it was the king he bought his followers to rampage around the castle. What proof does he have it was the king? None. How does he know the king is being truthful when he accuses Hamlet? He