I think that evil is probably best represented through Goeth.  The movie does an excellent job of being able to contrast the battle of wills between Schindler's side of seeking to indulge himself, moving himself closer to where Goeth is, and embracing a life of virtue, which will result in extreme personal sacrifice.  The evil that is shown in the film is the result of self interest gone awry.  Goeth is motivated only by his own desire to be supreme as well as advancement of his own sense of self.  His indulgences in this domain result in evil being perpetrated.  We never get the impression from the film that Goeth is someone who does what he does in the name of belief in Nazi ideology.  Rather, it is only through the indulgence of self interest that Goeth engages in what he does and this is where evil resides. The beatings he perpetrates, the cruelty he displays, and the manner in which he does these things only reflect his own sense of individual self. The display of evil we see in the film is one where individual desire is fed and nourished at the cost of social solidarity or social understanding of larger and more collective notions of the good.