Out, out, brief candle! /Life's but a walking shadow, a poor player, /That struts and frets his hour upon the stage, /And then is heard no more. It is a tale /Told by an idiot, full of sound and fury, /Signifying nothing." (IV.IV.19-28)
This soliloquy is perfect for showing the repercussions of unchecked ambition. Macbeth has put so much energy and time into becoming as powerful as he possibly can only to lead him to feel miserable, unfulfilled, and as if his life no longer has any purpose. Another soliloquy that displays unchecked ambition is also by Macbeth. "Glamis thou art, and Cawdor; and shalt be /What thou art promised: yet do I fear thy nature; /It is too full o' the milk of human kindness /To catch the nearest way: thou wouldst be great; /Art not without ambition, but without. /The illness should attend it: what thou wouldst highly, /That wouldst thou holily; wouldst not play false, /And yet wouldst wrongly win: thou'ldst have, great Glamis"