John Proctor is the protagonist of The Crucible, by Arthur Miller. In this story, Proctor has one major trait that brings about his demise: his lust for Abigail, a girl who works for him. Abigail and John embark on an affair, which ends up ruining his reputation. Although Proctor tries to hide the affair at first, he eventually realizes that he is facing his own demise as his wife Elizabeth is arrested.
Proctor's actions are consistent with those of a tragic hero. A single character trait led Proctor to make a series of bad choices, and in a context where reputation is everything, his damaged image cannot be expected to make a comeback. These actions are his downfall.
