What quotes show what kind of leader Macbeth is??

First, when Macbeth hires the murderers to kill Banquo and Fleance, these men claim that their terrible lives have hardened them to the world.  One says, "I am one, my liege / Whom the vile blows and buffets of the world / Hath so incensed that I am reckless what / I do to spite the world" (3.1.121-124), and the other, "And I another / So weary with disasters, tugged with fortune, / That I would set my life on any chance, / To mend it or be rid on 't" (3.1.125-128).  In other words, these men's lives have become so wretched under Macbeth's rule that they are made reckless: they are willing to take any chance to strike back at the world that has beggared them or to improve their lots.  This is the Scotland of Macbeth's reign: she is ruined, and its people ruined with her.  He is a terrible leader.

Later, Lennox calls Macbeth a "tyrant" when he speaks to another lord in Act 3, scene 6 (3.6.25).

Then, when Macduff goes to the English court to try and convince Malcolm to return to Scotland and reclaim the throne, he says that "Each new morn / New widows howl, new orphans, cry, new sorrows / Strike heaven on the face, that it resounds / As if it felt with Scotland, and yelled out / Like syllable of dolor" (4.3.5-9).  In other words, Macbeth is so tyrannous that men seem to disappear in the night, leaving their wives to wake up husbandless and their children fatherless.  Life in Scotland is so bad that Macduff feels heaven must cry out as the Scots do under Macbeth's regime.

When Ross comes to tell Macduff about Macduff's murdered family (killed under Macbeth's orders), he says, "Alas, poor country, / Almost afraid to know itself.  It cannot / Be called our mother, but our grave  [...] Where sighs and groans and shrieks that rent the air / Are made, not marked" (4.3.189-194).  Macbeth has been such a terrible leader that Scotland has become a grave for the Scots instead of the nurturing mother she seemed to be under Duncan's reign.  People cry and scream, but nobody even pays attention anymore because those sounds have become so commonplace.