In the novel, who is a worse character: Luke O'Neill or Ralph De Bricassart?
The answer to this question largely depends upon one's perspective. Although it can be said that both ambitious men take undue advantage of Meggie, Father Ralph De Bricassart at least claims to love Paddy Cleary's only daughter. Yes, it is true that both men lust after Meggie, but Luke O'Neill has the distinction of being a crude and selfish husband to the one woman he has promised to protect and to cherish. Father Ralph, on the other hand, is Meggie's trusted mentor for all of her awkward and difficult childhood years. In adulthood, Father Ralph ironically becomes the only man who can satisfy her sexual and emotional needs. Alas, as Meggie complains, although Father Ralph 'wants' her, he never manages to fully accept his need for her and ultimately ends up disappointing her.
As the story goes, the spiteful Mary Carson bequeaths her entire estate to the Roman Catholic Church, with Father Ralph De Bricassart as executor. Worth over thirteen million pounds, Mary was a very successful businesswoman when she lived. Her lust for Father Ralph De Bricassart had been consuming then, and in death, she managed to exact her vengeance on him for rejecting her sexual advances. For his part, in order to realize his goal of ascending the hierarchy of the church, Father Ralph refuses to contest the contents of Mary's new will. Faced with a choice between Meggie's welfare and his own, Father Ralph selfishly chooses to satisfy the dictates of his own self-interest.
Luke O'Neill is similar in that he marries Meggie for her wealth; for all his alpha confidence, Luke's selfishness and insensitivity to Meggie is revolting to our senses. After their wedding, he appropriates Meggie's twenty thousand pounds for his own, telling her that he is an old-fashioned man who thinks that a wife's property automatically belongs to her husband. Luke tells Meggie that he is saving up to buy his own sheep station and maintains that he doesn't want to be the type of husband who lives off his wife. However, his actions contradict his words.
To add insult to injury, Luke is what Meggie calls a 'skinflint.' In fact, he is such a miser that he purchases two second-class, upright seat tickets for the three-day journey to Dungloe for their honeymoon. When Meggie protests, his reply is breathtakingly unsympathetic:
"Why spend money on a sleeper when we're both young, healthy and strong? Sitting up on a train for a while won't kill you, Meghann! It's about time you realized you've married a plain old workingman, not a bloody squatter!"
After the three-day journey, Meggie is exhausted and bewildered by the cruel disregard of her new husband. However, Luke is unperturbed by his bride's discomfort and despair. In fact, he complains bitterly that he was cheated out of his wedding night because his bride slept for two days straight after the arduous journey.
When the two finally manage to consummate their marriage, Luke is rough, callous, and selfish. His primary goal is the fulfillment of his own sexual desires. Because he doesn't take the trouble or the time to prepare Meggie for his eventual forced entry, Meggie suffers horrific pain and discomfort. Far from displaying any sort of sympathy for his innocent bride, Luke exhibits anger at her inexperience and fear. This leaves Meggie wishing for death so that she can be spared further humiliation and physical agony.
After the satiation of his desires, Luke loses no time in telling Meggie that she will be hired out as a maid of sorts to the Muellers at Himmelhoch. Ludwig Mueller is a man Luke calls a 'cane cocky,' the owner of a cane plantation. Meanwhile, Luke asserts that he himself will join a group of sugarcane cutters in North Queensland. Before he leaves, he makes sure to appropriate all of Meggie's pocket money and savings for his own. Even Meggie's future wages will be directly paid into his account. In short, Meggie is to have no money of her own and no ability to effect her own future.
Of course, the above describes only a few examples of Luke's avaricious and selfish conduct. On the other hand, even though Father Ralph controls Meggie's financial future as executor of Mary Carson's will, he generously provides for Meggie and her immediate family. Accordingly, Father Ralph deposits seven thousand pounds into Paddy Cleary's account and opens up savings accounts of two thousand pounds each for every member of the family. Additionally, Meggie and her whole family will have assured incomes of thousands of dollars each for every month they work at Drogheda. For Meggie, the money is still assured even if she chooses not to live and to work on the family property.
So, although Meggie never realizes true happiness with either man, Father Ralph at least attempts to provide for Meggie's immediate needs. Yet, because they are ambitious men, one can say that both ultimately fail in their duty to Meggie. In order to answer your question, you may have to choose who you think represents the greater evil in Meggie's life.