Answer:
The given quote means that Malcolm doubts if the people will really want him to be king of Scotland after Macbeth. He thinks that when his <em>"confineless harms"</em> are compared with the acts of Macbeth, then "<em>black Macbeth Will seem as pure as snow</em>" to the people.
Explanation:
This speech by Malcolm in the play "Macbeth" by William Shakespeare is from Act IV scene iii. The scene shows Macduff and Malcolm in conversation, with Malcolm telling his friend that he did not trust him and thinks he may have been a spy for Macbeth.
But aside from all these, Malcolm expresses his concern about himself and wonders if he is rightfully fit to rule Scotland. He exclaims "<em>my poor country Shall have more vices than it had before, More suffer, and more sundry ways than ever, By him that shall succeed.</em>" Macduff tried to convince him by telling him that "<em>Not in the legions Of horrid hell can come a devil more dam ned In evils to top Macbeth.</em>" The given quote excerpt in the question is Malcolm's doubts about himself and his reluctance to take after Macbeth as king of Scotland, for he fears that the people will compare him to Macbeth and find that his (Malcolm) sins and evil deeds are far more worse than Macbeth's.