Laertes and fortinbras are two characters in shakespeare’s play that serve as foils for hamlet. how does each figure expose or highlight certain traits in hamlet’s character, and how does each character’s behavior in the play relate to the themes of advice and duty, action versus inaction, and sanity versus madness?

 Fortinbras's father was killed by Hamlet's father 30 years earlier. Fortinbras is an evil coward who didn't try to recover the lost lands until after Hamlet Sr died. If Fortinbras had attacked while old King Hamlet was still alive, the old King might have challenged young Fortinbras to a personal duel. But young Fortinbras was a coward who preferred to send thousand of commoners to die for his rotten royal "honor." So after old King Hamlet finally died, young Fortinbras "sharked up" an army of thugs to go to war against Denmark, but was easily diverted (at least temporarily) to easier pickings in Poland. In Poland, Fortinbras sent 10,000 men to their graves for a worthless piece of land. 

Laertes, when he thought King Claudius had killed his father, immediately confronted the King - but with a mob to back him up (and possibly to die for his cause). After hearing Claudius side of the story, Laertes immediately began plotting with Claudius to kill Hamlet by treachery. He didn't care about right or wrong, he just wanted revenge, even if it meant cutting Hamlet's throat in a church. He didn't bother to hear Hamlet's side of the story. However, just before the duel Laertes did finally hear Hamlet's apology which he would have accepted but he foolishly deferred to the opinions of "elder masters" - meaning Claudius - and continued the duel against his conscious. Laertes's father had warned him 

Neither a borrower nor a lender be; 
For loan oft loses both itself and friend, 
And borrowing DULLS THE EDGE of HUSBANDRY. 

But Laertes ignored that advice. When plotting to murder Hamlet, Laertes said "for my means, I'll HUSBANDRY them so well, They shall go far with little." Then Laertes died fighting for a borrowed cause (borrowed from Claudius, his "elder master"). In a sense, he was killed because of borrowing and lending of swords (the accidental switch between swords, one poisoned) and that loan lost "both itself and friend (both Laertes and Hamlet, who was his friend at the end). However, before he died Laertes and Hamlet exchanged forgiveness and thus saved both their souls. 

Hamlet wasn't naturally vengeful, but he was loyal to his father so he swore an oath to his father to seek revenge. But Hamlet didn't want to endanger his friends in the dangerous mission of seeking revenge against a sitting King, so he urged his friends to "shake hands and part." In the last act, he returned to Denmark "naked and alone" to confront the King. Hamlet was very concerned about right and wrong. Not sure that the ghost was really his father rather than a deceitful demon, he staged the Mousetrap to verify Claudius' guilt. In the last act, Hamlet realized that, in pursuing revenge, he had been untrue to himself - had written his father's command to live all alone in his brain. He had from himself been taken away and that was madness. A common theory of madness was that it was caused by demonic possession. At least psychologically and metaphorically, Hamlet had been possessed by his father's spirit. Hamlet recovered his true self by the end and saved his soul, but not his life.