In accordance with the above post, Ophelia's naive, pure character acts as a foil to the corrupt characters of Claudius, Gertrude, Polonius, Rosencrantz, Guildenstein, and others of the Danish court. It is no mere venomous refrain that Hamlet issues Ophelia when he charges her to "get thee to a nunnery. Why would thou be a breeder of sinners?" (III,i,119). She is not like his mother, whom Hamlet perceives as having both betrayed his father and incestuous in her lust.
It is also no coincidence that Hamlet's lashing remarks in Act III follow his famous "to be or not to be" soliloquy in which he has wrestled with morality and the expediency of avenging his father's death. After his "perusal of [Ophelia's] face"(II,i,89), and his raising a sigh so "piteous and profound," (II,i,93) the contrast of the purity of Ophelia reminds Hamlet so much of the degenerate behavior of others, that he orders her away having recognized her vulnerability.
Three adjectives and a noun to describe Ophelia: ingenuous, naive, guillible, and a foil to the other characters.
Ophelia is a character of purity, trust and innocence in Hamlet. She stands in marked contrast to the schemeings and manipulations of the Danish court. Ophelia has been shielded by the love of her father Polonius and has been in love with Hamlet from before Hamlet's tragedies occur. Since she is all innocence and trust, she is frightened and disillusioned by Hamlet's inexplicable behavior and persuaded by her father's urgency in the need for her to help establish what Hamlet's condition and motives are. When death and woe, which are far too much for her to bear in her shielded innocence, surround her, her mind breaks under the burden of the realization of the uncharitable and cruel realities of the Danish court. She is found dead in the water and no one knows for sure whether it was by her own hand or by accident.
The four key words are: innocence, purity, trust, vulnerability.