Here's why:
* Exploitative Nature: The doctor is initially dismissive of Kino's illness and only agrees to treat Coyotito after Kino finds the pearl. He charges exorbitant fees, knowing Kino is desperate and unaware of typical prices.
* Hypocrisy: The doctor claims to be "a man of science" but is willing to exploit a poor family for his own gain. He even uses religious justifications to rationalize his greed.
* Lack of Compassion: The doctor shows little empathy for Kino and his family, particularly after Coyotito's death. He represents a system that prioritizes profit over human life.
While other characters like the priest and the pearl buyers also exhibit greed, the doctor's actions stand out due to their direct impact on the well-being of Kino and his family.
It's important to note that greed is a complex theme in the story, and other characters, like Kino himself, are also susceptible to its influence. However, the doctor's greed is presented as particularly insidious and exploitative, making him the most prominent example in the novel.