Discuss Krogstad's character in A Doll's House.

Initially, Krogstad is the play's antagonist. He comes across as a thoroughly dishonest character, with a track record of fraud in his financial career. It's not surprising, then, that he should try and blackmail Nora over her fraudulent loan application in which he played a leading role. Krogstad is a bitter man, angry over how life's treated him. He missed out on marriage to Kristine Linde due to a lack of money, and this ultimately proved to be the catalyst for his descent into moral corruption.
Yet as the play progresses, Krogstad shows he has the ability to change. Thanks to the rekindling of his relationship with the widowed Mrs. Linde, his perspective on life changes. The love of a good woman forces him to take stock of his life, to realize that his behavior towards Nora was morally unacceptable. He still wants Nora to face up to the truth of what she did, not out of a thirst for vengeance, but because he genuinely wants her to experience the kind of moral transformation that he has undergone due to the love of Mrs. Linde.