Final answer:
Laertes consents to Claudius' scheme primarily out of a deep grief and desire for revenge for his father's death and sister's madness, which Claudius attributes to Hamlet's actions.
Step-by-step explanation:
Laertes goes along with Claudius' plot because he is mad with grief over his father's death and seeks revenge against Hamlet whom Claudius implicates in Polonius' death and Ophelia's subsequent madness. Deeply troubled by these events, Laertes is driven by a strong desire for vengeance and is easily swayed by Claudius' manipulative tactics.
This need for retribution is a powerful motivator and leads Laertes to agree to the king's sinister plan to kill Hamlet, which includes a fencing match rigged with a poisoned tip sword and a backup plan involving a poisoned drink.
Laertes' hatred towards Hamlet escalates further due to the prince's role in his sister Ophelia's madness and death. The complex dynamics of grief, revenge, and manipulation are pivotal to understanding Laertes' actions in Shakespeare's tragedy Hamlet.