Final answer:
Malcolm is stating that Macbeth and Lady Macbeth were evil characters who caused chaos, leading to their downfall.
Step-by-step explanation:
At the end of Shakespeare's play, when Malcolm refers to Macbeth as 'this dead butcher' and Lady Macbeth as 'his fiendlike queen,' he means that they were both evil and caused chaos throughout the play. This characterization comes after Macbeth and Lady Macbeth's ruthless ambition led them to murder King Duncan, among other atrocious acts, to ascend to power. Their actions brought turmoil and tragedy to Scotland, ultimately leading to their own downfall.