What is the best example from Macbeth that shows how severely Macbeth loses his morals?

Since this is an opinion question, I have two possible answers.

I’d argue strongly for Macbeth’s decision to slaughter Macduff’s wife and children. Since the witches tell Macbeth to “beware Macduff,” Macbeth’s suspicion of Macduff is justifiable. I bet that many readers would even argue that Macbeth would be acting rationally if he attempted to capture or imprison Macduff. However, Macbeth had no reason to fear Macduff’s wife and children. By indiscriminately executing them, Macbeth showed that he can no longer control his paranoia and prefers to target the innocent rather than fix the true source of his problems.

I’d also like to point you towards Macbeth’s reaction to his wife’s suicide. He says, “She should have died hereafter. / There would have been a time for such a word” (5.5.17-18). Many commentators interpret this as “Well, she would have died anyway.” It’s a caustic and sarcastic response to the death of his wife that shows his complete apathy towards human life.