Greed is portrayed by Conrad as an integral part of the colonial project. It doesn't simply relate to the unscrupulous actions of a handful of greedy individuals; it's part and parcel of what it means to be a European colonialist in Africa. Whatever the Belgians and other colonists might say, they didn't come to Africa to bring the benefits of Western civilization to the poor, "benighted" natives: they came in search of riches. In search of those riches, they will do whatever it takes in order to achieve wealth—however brutal or degrading.
In Heart of Darkness, greed can be observed as corrosive to the soul—undermining whatever high moral standards or elevated notions of civilization the colonialists may have once shared. In one particularly revealing scene, Marlow makes a casual remark about the cannibalism of the men he's hired to help him aboard the ship. Back in England, the very idea of eating human flesh would be considered taboo, but out in the Congo, traditional Western values have been subverted by the imperatives of colonialism, which have manifested from greed.
All that matters to Marlow at this precise moment in time is that his hired shipmates can help him in his quest for riches. The fact that they also happen to be cannibals is of no importance to him whatsoever. So long as they don't eat each other in front of him, he doesn't really care.
Conrad represents greed by depicting the unscrupulous means the Company's employees exercise to attain massive amounts of ivory and increase their professional statuses. The Company itself is portrayed as an oppressive, inefficient bureaucratic machine used to collect foreign resources while simultaneously destroying and destabilizing native African societies. Marlow witnesses firsthand the effects of the Company's greed when he visits the various European stations established in Africa. Conrad also represents greed by depicting the immoral, conniving agents, who lie, cheat, and steal from the Natives and other employees to increase their personal wealth and status. For example, Marlow meets the General Manager; he is a greedy man hoping that Kurtz will die so that he will be the next man in line to gain the Company's recognition. He even sinks Marlow's ship to prevent Kurtz from receiving medical aid and necessary supplies. The character of Kurtz also represents the corrupting nature of greed. Marlow discovers that Kurtz is viewed as a god by the natives and conducts raids on other villages to attain large quantities of ivory. Kurtz's insatiable greed corrupts his soul, and he is responsible for committing unspeakable atrocities to increase his wealth and status. Overall, the Company and its agents are fueled by greed and completely destabilize and oppress the various African societies.