Nils Krogstad is an antagonist of the play. He is an unscrupulous and dishonest. He blackmails Nora, who borrowed money from him with a forged signature, after learning that he’s being fired from his job at the bank. In the past, he too committed the crime of forgery, an act that he didn’t attend prison for but that nonetheless ruined his reputation and made it extremely difficult to seek out a good job. Later in the play, it’s revealed that he was once crazy with Kristine Linde, who ended up marrying another man to possess enough money to support her dying mother and young brothers. This left Krogstad lost and embittered, unhappy in his marriage, and is presented because of the reason behind his moral corruption. Initially, he treats Nora without mercy on the idea that no mercy has been shown to him in life; however, after he and Mrs. Linde plan to marry, he becomes happier and rescinds his threats to Nora, saying he regrets his behavior. he’s one among several examples within the play of an individual being forced into morally questionable action as a result of the rigid and unmerciful forces of society.