We Have Scorched The Snake Not Killed It
What does the quote "We have scorched the snake, not killed it: ...Remains in danger of her former tooth," mean in Macbeth?

We have scotch'd the snake, not kill'd it.(15)
She'll close and be herself, whilst our poor malice
Remains in danger of her former tooth. (Act 2, Scene II)

Macbeth tells Lady Macbeth that, by killing Duncan, they have not put the matter of the throne to rest. By scorching the snake but not killing it, Macbeth means that they still have threats to face, even with Duncan out of the picture. He also references that they have put Duncan to rest in peace, while they must still suffer through challenges so long as they are alive. Macbeth's mounting guilt has made him increasingly paranoid, and he worries that his place on the throne, as well as his life, is not secure.

By scorching the snake but not killing it, Macbeth means that they still have threats to face, even with Duncan out of the picture.

Explanation:

William Shakespeare's Macbeth deals with the story of Macbeth who, adamant on making his fate come true from the prophecy of three witches, did numerous evil acts. Added to that, he was also led to these murderous acts by his equally power hungry wife Lady Macbeth.

The given excerpt from Act II scene ii of the play reveals how Macbeth feels even after getting rid of his primary enemy King Duncan. Even after assurance from his wife to relax, he did not seem happy about his act. Rather, he wanted to get rid of anyone who seems an obstacle for his road to the throne. Scorching the snake is a metaphorical way of indicating the removal of one stumbling block, but "not kill'd it" shows that he still believes there are more threats before he could successfully and happily sit in the throne. Duncan's death may be what he wanted, but it is not the end of any threat. The snake is the whole entity of the possible threats, and the scorching act is just the start of getting rid of the whole animal. The snake is a metaphor for all threats.

c. there are many strengths