A good person would, by definition, not make 'mistakes'; they would be perfect in everyway.
Case in point, let's discuss what it really means to be fallible, to be flawed: The men who guarded the concentration camps, who dropped the zyklon b gas tablets - would we not agree their environment determined what they did, who they were, on some level? There was a set of circumstances wherein, they did not merely wrong, but terrible wrong.
Now, the question exists: if you were put into the same circumstances as them - raised in the nazi youth, trained to hate jews, to kill the fuhrer's enmies, etc. - would you not do the same?
either we will conclude that we, personally, are supermen, ethically impervious, and totally superior, that we could do no such thing regardless of our circumstances - but of course, that is what Nazis believed, and this kind of believe in innate superiority over others has been the father of most modern genocides.
Or we can admit, frankly, if we were in their place, we too would be ravaging murderers, rapists, that the only thing keeping us from being all that and worse is the mercy of our circumstances: but for the grace of God there goes I.
So what would be a "good" person? he would be a perfect man, the man who really cannot be tempted to do evil regardless of the circumstances. It would not matter what temptation or pressures arise, this man would be truly impervious to the intent to do evil.
And so we must admit we are not that man, and that we, then, are evil. After all, if the only thing keeping us from being monstrous is circumstance, we must either admit one of two possibilities: either that those who did those monstrous things such as the Holocaust, Rape of Nanking, Armenian and Rwandan genocides, My Lai Masscre, Parsley massacre, Holodomor, etc. were not evil at all (and perhaps good and evil do not even exist!) or we will have to admit we too would have done such things if our circumstances were different, and therefore we are surely no better than those who did do such things.
“As the folk saying goes: If you speak for the wolf, speak against him as well. Where did this wolf-tribe appear from among our own people? Does it really stem from our own roots? Our own blood? It is our own. And just so we don’t go around flaunting too proudly the white mantle of the just, let everyone ask himself: ‘If my life had turned out differently, might I myself not have become just such an executioner?’ It is a dreadful question if one really answers it honestly.”