The main similarity between the two of them is...
In both Macbeth and “The Laboratory” we have a very ambitious woman who is willing to resort to murder to accomplish her ends. Both women are not afriad to kill, both use a lot of descriptive language, and both are planners.
The main similarity between the two of them is that both are open to murder and neither has any moral problems with it.
In “The Laboratory” the narrator describes how she is going to kill her lover’s mistress.
NOW that I, tying thy glass mask tightly,
May gaze thro' these faint smokes curling whitely,
As thou pliest thy trade in this devil's-smithy--
Which is the poison to poison her, prithee? (poem hunter)
Compare this to Lady Macbeth’s description of killing Duncan.
Come to my woman's breasts,
And take my milk for gall, you murdering ministers,
Wherever in your sightless substances(50)
You wait on nature's mischief! Come, thick night,
And pall thee in the dunnest smoke of hell… (Act 1, Scene 5, p. 20)
She does seem to show some remorse at this point in hoping that her “keen knife see not the wound it makes” (p. 20). She does not show any remorse again until the end, when she is wracked with guilt and loses her mind.
Another way the two women are similar is that they are both very descriptive. Lady Macbeth often creates very disturbing images.
I have given suck, and know(60
How tender ’tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out …(Act 1, Scene 7, p. 24)
As she describes how she would nurse a baby and then dash its brains out, we have little sympathy for her. Likewise, we do not much sympathize with the deranged narrator in “The Laboratory” who is planning to actually poison her lover and his mistress.
Both women are planners. They devise clever plans down to the smallest detail. They think of everything in carrying out their terrible deeds.