There is a great deal of duplicity exhibited in Shakespeare'sHamlet. Characters are saying one thing and thinking something else. Hamlet himself is a good example of duplicity. He comes up with the idea of pretending to be mad because this will enable him to hide his true thoughts and motives from all the people who are trying to pry into his soul, including Claudius, Polonius, Rosencrantz, Guildenstern, Ophelia, and his own mother. This would connect with duplicity in revenge.
Even Ophelia exhibits duplicity while acting in obedience to her father's instructions to keep aloof from Hamlet and pretend to be indifferent to him. This would connect with duplicity in love. Hamlet loves her too, but he pretends to despise her.
Polonius is the soul of duplicity. He hides his true thoughts even from his son and daughter. He sends an agent to France to spy on Laertes when the boy is away at college. Polonius has been to the university himself and he knows what sorts of behavior can go one there. Polonius shows duplicity in every encounter with Hamlet, and his duplicity will end up costing him his life.
Gertrude shows duplicity toward her own husband, and she has probably been somewhat dishonest with him since they were married. She must have married him because she wanted to hold on to her position as queen. If she had refused his proposal, he would have married someone else. (He might have even married Ophelia! Why not?) Gertrude would have lost most of her power and privileges. At best she would have been kept on as a poor relation. She has to pretend to be in love with Claudius whether she is or not. Then when Hamlet kills Polonius in her room, she lies about the incident to Claudius.
Rosencrantz and Guildenstern are specialists in duplicity. From the beginning they pretend they are there to visit their friend Hamlet, when in fact they have been summoned there to spy on him.
Only the Ghost seems incapable of duplicity--although Hamlet suspects him of extreme duplicity in pretending to be his father but being the Devil or one of the Devil's agents in disguise.
Horatio is an honest man, but he is capable of some duplicity in conspiring with Hamlet against King Claudius in the business involving the play within a play.
Claudius, of course, is the master of duplicity. He has to hide his true self, his true thoughts and feelings, from everyone, including his wife, because of the terrible crimes he committed against his own brother and his own nephew. Hamlet enjoys doing things that make him lose his composure. The play within a play actually forces Claudius to run away and hide in his chambers. Hamlet can only penetrate Claudius's duplicity because he is the only one who knows his terrible secret.