The first impression we receive of Hamlet is this grief-stricken prince. He displays a mourning appearance.
Hamlet cannot overcome his father’s death, even though everyone around him seems to have gotten over it abnormally quickly. Hamlet's grief develops a tremendous anger in him due to the lack of feeling by those around him, and more significantly, by the cold-hearted actions of his mother, who married her brother-in-law within a few weeks of her husband's death. This act by Gertrude, whom Hamlet loved unusually greatly at one time, causes Hamlet to become completely torn by her promiscuousness, and feeds his fire by remembering the memories of his father’s love towards Gertrude.
The comparison Hamlet creates between his noble father and his “drunkard” step father/uncle causes Hamlet to develop disgust for Claudius and all of the behaviors associated with him.
Unfortunately for the innocent Ophelia, the actions of Claudius and Gertrude have also ruined Hamlet's thoughts and feelings towards women. Based on the letters and gifts Hamlet gave his Ophelia, it is apparent that he did love the girl, and likely felt those feelings of sweet devotion that his father felt for his mother. However, due to the recent tragedies that have scarred Hamlet, he turns on Ophelia and destroys her, with unimaginable cruelty.
As the play he has arranged for the king begins, Hamlet takes a much different persona with Ophelia, at first he hates her, than he wants to lie upon her lap. Some argue that this scene supports the theory that Hamlet is truly mad. That he is unable to control his own thoughts and feelings. He hates Ophelia one moment and wants to be with her intimately with her the next. However he once again, heartlessly mistreats her with demeaning and disrespectful behavior. Hamlet is fueled by rage and thoughts of Gertrude's betrayal and Ophelia is the only outlet for the hostility that he must keep secret from the king. The belief that Hamlet still genuinely loves Ophelia, and that his hunger for justice force him to behave the way he does, allows us to conclude that Hamlet is simultaneously heartless