The tragedy is that Macbeth was once a good person. There is evidence that he was a brave soldier, and a loyal subject. However, the witches twisted his mind and pushed him so that all he saw was his ambition, and Lady Macbeth too.
The most tragic thing about Lord and Lady Macbeth is that they truly love each other, yet they are the ruin of each other. For, in her desire that Macbeth be king, Lady Macbeth unsexes herself and becomes ruthless. Yet, she is visibly shaken at the resemblance of Duncan to her father and cannot herself commit the murder. Her conscience, then, weaker than her aspirations for her husband, causes her to go insane with her all-consuming guilt. Macbeth, too, commits heinous deeds because of his "vaulting ambition" while at the same time feeling guilt and, certainly, remorse at the untimely death of his wife: "She should have died hereafter;/There would have been a time for such a word."
I agree with mwalter822. If you consider Macbeth at the beginning of the play, his potential, his loyalty, his strength and his morals, then look at what he becomes in the end. He is a shadow of his former self.
Also look at Lady Macbeth, her desire for power leads her to a very quick downfall. In the end, all her conniving qualities only lead to her husband's changes and never to any power for herself. She becomes tortured with guilt rather than a Queen as she imagines.
Think about what it is the Macbeth and Lady Macbeth want out of life as the play opens. Then what do they do to get what they want? Finally, how do the feel about their actions, and how do they feel at the end of the story? You'll find the tragedy in the answers to those questions.
the most tragic about their life is that they have the right ambition ( because everyone want the best for themselves ) but they have accomplished it in a wrong way. If we consider Macbeth's tragic flaw it would be his ambition also i would definetely say that the more appropriate for Macbeth's tragic flaw is his weakness of character that he couldn't make out his own decisions though somewhere he knew microcosmically that what he is gonna committ is absolutely wrong but still he relied on Lady Macbeth's advices. And for lady the most tragic is that she wanted good for her husband but she brought out it to be worse for him