"That no compunctious visitings...and it!"

Definition: Please see notes below.

Lady Macbeth. That no compunctious visitings of nature
Shake my fell purpose, nor keep peace between
The effect and it! (1.5.50-3)

i.e., That no forces of goodness ('nature') invade my conscience and stop me from proceeding with my cruel intention ('fell purpose') of trying to murder Duncan, nor interfere ('keep peace') with the actual outcome of the attempt.