In Act III, Hamlet is shown in an overall negative light.
There can be justifications behind why Hamlet does what he does. However, Shakespeare uses Act III to display much of his capacity for cruelty. An example of this would be in his treatment of Ophelia. His "get thee to a nunnery" and then openly flirting with her in the very next scene are examples of how he is shown in a negative light. In the process of mistreating Ophelia, Hamlet makes statements that denigrate all women, adding to the overall negativity surrounding him. He might be "cruel only to be kind." However, the second part is difficult to see.
Hamlet commits murder, and engages in verbal abuse of his mother: "If you tell your husband that I'm only pretending to be crazy, your neck might break, which would be most unfortunate." There is an intentional malevolence shown within his character in Act III. Hamlet is replicating the very same evil that he criticizes. His hatred of the evil killed his father has replicated itself and is manifested in his treatment of others. He is shown to be very harsh to other people and incapable of restorative emotions.
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