In Dracula, Bram Stoker sets up a contrast between good and evil that persists throughout the story, which is represented by Mina Harker and Dracula. Before Mina makes her speech after the men return from their failed attempt at capturing Dracula, Dr. Seward writes a commentary on her appearance and character (Stoker 328). He opens with an observation of “that sweet, sweet, good, good woman in all the radiant beauty of her youth and animation.” The pronounced repetition of “sweet” and “good” drives home the idea that Mina is the most pure, innocent, perfect woman. Throughout the story, Mina is presented in this idealized light; she can do no wrong, and she is adored by all who surround her because of her everlasting kindness and devotion to her friends. She represents a double symbol within the book: she epitomizes both the concept of pure goodness and the idea of the perfect woman.
Mina’s foil is Dracula, who embodies evilness. While Dracula is a centuries-old, Undead, foreign vampire, Mina is a young, healthy, properly English woman. Throughout the story, these characters remain perfect opposites, but the lines between them are blurred when Dracula begins to feed on Mina. This relationship is solidified when Mina is branded with the sacred wafer, leaving a glaring red scar on her forehead. This scar serves as a symbol of Mina’s “taintedness,” how her perfect purity has been marred by evil. The scar itself is explicitly recognized as a symbol by Seward, who writes, “we, knowing that so far as symbols went, she with all her goodness and purity and faith, was outcast from God.” Even though Mina is still just as kind and loving as ever, the scar has marked her as impure and has thus made her unholy. This binds her even more closely to Dracula, who has been established as an anti-God character throughout the novel.
Dracula and Mina’s foil pairing and the tragedy of their connection represent the Victorian fear of the invasion of the foreign as a threat to the purity of English women. More broadly, it represents the contrast between good and evil, specifically in the context of religion. Stoker presents the fall of Mina, and her eventual redemption, as a word of warning that pure goodness must be protected from the unholy touch of evil.
I think that this contrast of good and evil is present in a lot of the poems and novels we’ve read. Dracula and Mina share a strange connection of purity vs. evil, which like you said almost give us this religious aspect. This is like Dr. Jekyll and Mr. Hyde. In the beginning chapters of the novel, Dr. Jekyll comes off as this relatively friendly nice man and is always apologizing for Mr. Hyde or denying any sort of negative interaction that those two could have had. Then there’s Mr. Hyde who is described as mad (for starters), but also as “something displeasing, something downright detestable” (5). This while it doesn’t necessarily have the ties to God, shows a kind of purity of Dr. Jekyll in that he seems like a good man and is liked by most, but then there’s Mr. Hyde who has likely murdered someone (anger issues…) and is extremely antisocial and “displeasing” to others, creating these “perfect opposites” as you said.
I think your distinction between Victorian representations of good and evil also relates to physiognomy and obsession with appearance. The scar on Mina’s forehead from the wafer depicts her close encounter with evil, non-holy forces, physically reducing her “radiant beauty” (Stoker p. 328). Similarly, Hyde’s appearance is marked with such evil, non-holy forces, described as having “Satan’s signature upon a face” (Stevenson p. 10), resembling some kind of deformity discussed by both Utterson and Enfield. I tend to take a 21st century critique of this as ableist, because it associates physical abnormalities with devilishness, and thus impurity and evilness. I don’t think this level was present in Dracula, although that text may have had more sexist undertones.