Malcolm, making the final speech of the whole play, says that tyranny produced
... the cruel ministers
Of this dead butcher and his fiend-like queen,
Who, as ’tis thought, by self and violent hands
Took off her life...
Macbeth's murdering ways make him a "butcher", though - as many critics have pointed out - the power of his soliloquys and poetic imagination make this a deeply reductive verdict which reminds us what Macbeth looks like if you don't hear his soliloquys.
And Lady Macbeth, of course, in this verdict has become what she asked the "spirits" in her first scene to make her become: a devil, a fiend, and one without remorse. This is, incidentally, also the first time we learn that Lady M has actually killed herself: we knew that she was dead, but not the how.
Hope it helps!