The wrong father
Xan hates a man named Joseph Andrews, but in an irony twist, it is revealed that the man he has hated his whole life is actually his own father. Their story seems to be the karmic aftermath of Andrews' failure to raise his son. In the end, he damages his own son permanently, and it incurs his own death. Therefore, Andrews is an ironic father, a kind of anti-father, so to speak.
The irony of Cora's failure
When Cora tries to manipulate Xan, she learns an ironic lesson—not everyone is manipulable. Because Xan has already suffered in such an extreme, permanent, existential way, he is not malleable to Cora, and as she slowly puts that together, she discovers empathy for him. The empathy drives her to be mentally disturbed—she tried to use him when he was literally at his most vulnerable, and that knowledge is difficult to bear.
The irony of Smoker's decision
Smoker ironically condemns himself by his own judgment. By deciding that Xan's injuries warrant vengeance, he accidentally defeats his own argument by making use of the same tool he is judging Andrews for—violence and terrorism. By imposing his own judgment as moral law, and by executing judgment against Andrews and his men, Smoker ironically fails ethically, showing that violence spreads like wildfire when vengeance is sought.
The irony of life and death
Instead of creating a new life with a loving wife, Andrews abandons his son to a difficult life, and that literally sets off a chain of events that leads ultimately to Andrews own murder. This is ironic, but it's also kind of karmic, because Andrews irresponsibility leads to his own downfall, but ironically, it also happens to be a similar fate to the one he unknowingly inflicted on his son.
The irony of existence
The novel is showing the reader that sometimes, we perceive reality wrong. The novel portrays a list of characters who all fail in the same way—they don't consider the broader effects of their actions, and without a proper sense for the true consequences of their actions, they set off chain reactions that ultimately lead to them learning a painful lesson, the hard way.
