In Graham Greene's Brighton Rock, what impact does Pinkie's judgmental attitude towards Rose and "sinners" (those who smoke and drink) have on him as a character (and his demise) and the novel in general?
Oh my, Pinkie is nothing if not judgmental (and hypocritical)! This is mostly seen in his contrast with the character of Ida Arnold.
You see, Ida Arnold is interested in the morals of society while Pinkie is interested in the morals of a warped form of Catholicism. Ida has no issues with drinking or smoking, but has a great sense of compassion (note how she always wants to protect poor Rose from all of Pinkie's tricks). In contrast, Pinkie has no compassion at all (as we can see with his participation in and reaction to Hale's murder). Further, he has been sexually repressed in an effort to be "holy" while participating in horrid gang violence.
While Pinkie is being judgmental he unwittingly falls into a trap of immorality. In addition to the gang violence, there is the false reasoning behind the marriage with Rose, another Catholic, who Pinkie only marries to protect himself. Further, he makes a suicide pact with Rose (after she announces that she might be pregnant); he plans to have Rose go through with it while he will be set free as a result of not keeping his side of the pact. We learn the truth behind this in the wedding gift tape:
God d**n you, you little b***h, why can’t you go back home forever and let me be?
How does all of this evil trickery and judgmentalism lead to Pinkie's demise? Simple. He sets up a convoluted trap that ends in his own "accidental" death. As Pinkie and Rose approach the cliff, Rose almost shoots herself in the head, but is surprised by footsteps. Pinkie is foiled. As the bottle of sulfuric acid (that Pinkie planned to poison Dallow with) breaks, spewing acid into Pinkie's own face, he falls off the cliff into the sea, dead as a doornail. It seems Pinkie's judgements have finally killed him off.
Unfortunately, the story ends with an astounding note of disillusionment because Rose, now saved from the evils of Pinkie, is destined to live out hell on earth when forced back into the arms of her aloof parents, bereft of compassion for Rose's situation.