Which characters does Mary Shelley make the reader feel compassion for, and why, in the novel 'Frankenstein'?

One of the strengths of this novel, and there are many, is that Shelley wrote very complex characters. As a result, there are many characters in the book whom we feel compassion for:

The Monster: This is the most obvious one. Although he does some heinous things to get back at Victor, the reason he feels so sad and angry at Victor to begin with is because he has been completely abandoned by his creator and thrust into the world with absolutely nothing. Anyone and everyone he comes across treats him like a monster, and thus he becomes one. We can't help but feel compassion for how lonely and rejected he is.

Justine: She is wrongly accused, then executed for, William's death. She clearly had nothing to do with his murder, no motivation to hurt him, and could have been saved by Victor if he had been brave enough to say something...anything! We feel compassion for Justine because she is a true innocent. She does nothing wrong and pays the ultimate price, her life.

Elizabeth: She, too, is a complete innocent. In all of the descriptions of her, we get the impression she is a wonderful person. When we do see her ourselves, she is kind, loving, and loyal. We cannot help but feel compassion for her because she dies an unnecessary death brought on by Victor's actions, not her own.

William: He's also an innocent who dies needlessly. Although one could argue he was mean to the Monster, the counterargument would also be that the Monster jumped out and grabbed him with the intention of kidnapping him to make him a friend. What child wouldn't be scared and say something mean? So, we feel compassion for his situation - he is about to be kidnapped, cries out, and gets strangled. 

Henry Clerical: He's only ever a good and decent friend to Victor and he ends up dead as well. He does not deserve this, and again, we must feel compassion for this senseless death.

Victor: Although this is the most arguable person on the list, Shelley does cause us to feel compassion for him at times, especially toward the end of the novel. He has clearly made some significant mistakes in his life and he is sorry. His life is ruined, he has lost everyone he loves, and he can't do anything to fix any of it. We do feel some compassion for how terribly wrong everything went for him and, frankly, how naive he was to think it would go any better.