Perhaps the most obvious theme of King Lear is that power corrupts. In the story, the only three characters left standing at the end are Kent, Edgar, and Albany. They are also the only characters, besides Cordelia, who are not corrupted by power. Whether driven to betrayal or madness by power, the death of all the characters who fall victim to that fate sends a strong message about the consequences of power.
The case of Edmund is one of blatant betrayal in the ambitious quest for power. He betrays his brother, and then his father, all in his efforts to gain the status he is denied as a bastard. After tricking his father into believing Edgar has betrayed him, and Edgar into thinking his father is after him, Edmund makes clear his desire for power in his monologue of thought;
A credulous father and a brother noble,
Whose nature is so far from doing harms
That he suspects none; on whose foolish honesty
My practices rude easy. I see the business.
Let me, if not by birth, have lands by wit.
All with me’s meet that I can fashion fit.
Edmund’s desire for power and status outweighs his familial duty and decency of spirit, and he suffers the consequences, dying at the hand of the brother he betrays.
Lear is someone else who meets their end because of the corruption of power. As king, he has all the power one could dream of, and yet, he loses it all, along with his life, because the power drives him mad. At the beginning of the story, there are already signs of instability in Lear’s behavior, but the true catalyst of his mind going into chaos occurs with the actions committed by his daughters. Being so used to power, Lear is unable to deal with situations in which he has none. Perhaps the most impactful example in the story is when his eldest daughters, Goneril and Regan, both declare that they will not permit him to have an entourage if he wishes to stay with them. This occurs after Lear has already divided up his kingdom between them, believing their false words of love and respect. In response to the betrayal by his daughters, and in his own madness, Lear runs out into a storm. When asked by Kent to enter shelter from the storm, Lear replies,
Thou think’st ’tis much that this contentious storm
Invades us to the skin. So ’tis to thee.
But where the greater malady is fixed,
The lesser is scarce felt.
In other words, Lear claims that the harm placed upon him by his daughters outweighs the possible harm that could be done to him by a storm. When Goneril and Regan try to reduce Lear’s power, he sees it as a sign of betrayal. The value he places on power and “excess” is so great that his daughters trying to take them away is too much for him to bear.
These are just a few examples of characters in King Lear that are brought down by their desire for power. The moral of the story being that those who want power should not have it, for it can only lead to destruction.