In The Scarlet Letter, what are two symbolic images of good and evil that battle over Dimmesdale's soul?
As sometimes happens, I am not sure of what you mean by your question, but I will try.
In my understand, symbolic images don't "do battle." I think you are referring to the two forces that may symbolize the fight between good and evil that battle for Dimmesdale’s soul --- Chillingworth and Hester. Chillingworth is the more obvious. He is obsessed with the desire to get revenge of Dimmesdale for the wrong he has brought on Hester. He becomes the Leech, sucking the soul out of Dimmesdale, seeking not his death, but the prolongation of his agony. Dimmesdale is keenly aware of this evil. In Chapter 17, the forest scene, he tells Hester, “That man’s revenge has been blacker than my sin. He has violated, in cold blood, the sanctity of a human heart.”
The force for good in Dimmesdale’s life is, of course, Hester. The forest scene makes it clear that she has never stopped loving him and that he, could he face himself and say it, he knows that he has never stopped loving her. In this scene they touch for the first time in seven years, years where Hester has waited for him, hoping that they could escape, suffering and recovering alone, but always being there for Dimmesdale. She must be one of the sustaining forces in his life, a symbol of the love that was once the best thing in his life.
So the stage is set and the battle rages … and in the end neither force can win.
I see another symbolic polarization, too, between the forest and the pulpit (the scaffold from which he addresses the public)! When Dimmesdale is in public, his need to appear virtuous and perfect, to conform to the expectations of his congregation, makes him a lesser man than he really is or would be. He can't affront his own weaknesses, his own humanity, sacrificing truth for image.
Dimmesdale, ironically, is a better person in the shelter of the forest. I say 'ironically,' for it is there where he met Hester in the first place and had illicit sexual relations with her. When he is in the glen, we get a glimpse of the man Dimmesdale could be, if only he could cast off the chains of pride and fear. The interplay of light and darkness also has a role here; at one point, Pearl is shown bathed in dappered sunlight while Dimmesdale is recessed in the shadows.
Dimmesdale's sickness (cough) is another metaphor of the internal struggle within himself. It is symbol of the psychological and spiritual congestion sucking away at his soul. When he goes on walks with Chillingsworth (and doesn't that name make you shudder with a chill?), his condition is often worsenend from the effort (not to mention the bad company).
Two other images come to mind that represent Dimmesdale's battle between good and evil. The first is the scaffold, which appears in three critical scenes in the novel. During the first scaffold scene, Hester is on the scaffold and Dimmesdale questions her about the father of her child. He tells her that even if the father has to come down from a high place (Dimmesdale is conveniently standing above her on a balcony), she should reveal the child's father. As Dimmesdale feels more and more guilty over his sin, he keeps returning to the scaffold. During the second scaffold scene he sees the image of good that is battling for his soul. That image is the one of little Pearl, who mounts the scaffold and asks him if he will stand in the daylight and acknowledge her before the town. His response shows that he is still not ready to own up to his crime. He tells Pearl he will acknowledge her "at judgement day"--or at the end of the world. But finally, as Dimmesdale feels himself dying, he returns to the scaffold and finally does acknowledge Pearl as his daughter. Thus, as Chillingworth points out, the scaffold now has no more hold on him.
There is no symbolic image representing images of good and evil battling for Dimmesdale's soul in the novel. There are images of evil, for example the prison door, the scaffold, the "A", and the weed that grows from the heart of the man with secret sin that Chillingworth discusses with Dimmesdale.
Images dealing with good would be the rosebush, the symbolic significance of "the pearl of great price" in Pearl, and the natural imagery of the chapter "A Forest Walk." The battle changes as each character is, in some way, untrue to themselves.