In Shakespeare's Macbeth, Macbeth is at first perceived as a hero, but as time goes on and he is tempted by the witches' prophecies and his wife's ambitious nagging, he turns his back on his morals and sense of loyalty, and becomes a villain.
The first quote that shows Macbeth a hero is from Ross, who is reporting Duncan, the King of Scotland's reaction to Macbeth's valiant fighting on the battle field:
The king hath happily recieved, Macbeth, / The news of thy success...He finds thee in the stout Norweyan ranks, / Nothing afeared of what thyself didn't make / Strange images of death. As thick as hail / Came post with post, and every one did bear / Thy praises in his kingdom's great defence / And poured them down before him. (I, iii, 89-90, 95-99)
In this passage, Ross is explaining that Duncan has been happy to hear reports of Macbeth's performance in the midst of battle. It seems that Macbeth was surrounded by a great number of soldiers of the Norwegian army. Macbeth seemed not at all concerned. Over and over, the enemy attacked, but Macbeth continued to battle, undeterred, for the glory of his king, killing all who came near him.
There are many quotations that illustrate that Macbeth is a villain. The following is Ross's report to Macduff that Macbeth has had Macduff's family killed:
Your castle is surprised; your wife and babes / Savagely slaughtered: to relate the manner, / Were, on the quarry of these murdered deer, / To add the death of you. (IV, iii, 204-207)
[Macbeth] has no children. All my pretty ones?...Bring though this fiend of Scotland and myself; / Within my sword's length set him; if he 'scape, / Heaven forgive him too! (IV, iii, 216, 233-235)
In this passage, Macduff not only learns that his family has been destroyed completely, but that Macbeth had hoped to find him home as well, and have him killed. (Macbeth sent assassins.) Macduff prays that providence will bring Macbeth within sword's reach so that Macduff can exact his revenge.
The character of Macbeth shows how a good man can turn his back on what he knows is right and good, and become a vile black-heart.