Deciding on Assef’s resemblance to Luke O’Neill or Mary Carson will depend on the particular characteristics you think are more important, as he has similarities to both (as they do to each other).
Assef is portrayed as a person with few redeeming characteristics. Hostility and lust for power seem to guide all his actions. Even when he has a chance to take the high road, he instead chooses a path that is more likely to damage the other person. The only mitigating factors that the author suggests are Assef’s deep-seated anxiety over his racial and cultural heritage, and the effects of being imprisoned and tortured. He not only identifies with his German side but also reaches back into the country’s Nazi history, apparently believing that this heritage makes him superior. Assef comes across as a sadistic bully, rapist, and killer. Although he claims his political activities are “God’s work,” he seems to be using them to mask his personal ambitions.
Luke’s many negative characteristics include untempered ambition combined with sexual predation. Manipulative, coercive, greedy, and selfish, he is also irresponsible toward his child. Even during his marriage, he lives apart from his family for much of the time, preferring male company and what he perceives as manly activities in the Outback.
Mary is presented as more complex in her motivations and actions. From misguided sexual passion, she makes a priest the object of her obsession. Manipulative in the way she steers Father Ralph’s ambition, she is hypocritical in her alleged support of the Church as her true aim is to control him. Mary values power and material wealth, and seems detached from true emotion.
A comparison of either Thorn Birds character with Assef is complicated by the fact that, despite the numerous complexities with which the author endows him, he nonetheless seems irredeemably evil. In his hypocrisy and love of power, he resembles Mary more. In his sexual sadism and excessively masculine persona, he seems closer to Luke.