Karl Barth incurred wide criticism with the claim that after the fall the image of God in human beings is completely annihilated, which is a crucial premise for Barth's theological epistemology and ethics. This article pays special attention to Reinhold Niebuhr's criticism of this statement of Barth that in this way Barth excused human beings from the responsibility of seeking realistic relative goodness in his historical existence. Niebuhr insisted that after the fall the image of God in humans is not "annihilated" but only "corrupted"; the original righteousness that humankind has been created with still remains in the fallen mankind, which should drive him/her to seek as much goodness as possible here and now. Through an examination of Niebuhr's and Barth's anthropology and doctrine of sin, this article would firstly point out the great similarities in these two giants' thought; nevertheless there are deep disagreements in their theological approaches. After a theoretical evaluation of Barth and Niebuhr's anthropologies and their ethical implications, this article looks further into their actual political practice in that versatile age and points out how their theoretical differences led to their practical disagreements.