King Lear is perverse, or we may say tragically flawed, in his treatment of his favorite and most loving daughter, Cordelia. His flaw (or perversity) lies in his inability to distinguish between rhetoric (words) and reality. He unquestioningly believes the lies his two eldest daughters tell him about how much they love him, how important he is to them and how willing they are to do anything for him. For example, Goneril says:
Sir, I do love you more than words can wield the matter,
Dearer than eyesight, space, and liberty,
Beyond what can be valued, rich or rare,
No less than life, with grace, health, beauty, honor,
As much as child e'er loved or father found—
A love that makes breath poor and speech unable.
Beyond all manner of so much I love you.
However, when Cordelia, unhappy at how her sisters are lying, won't flatter him in similarly outrageous ways, saying only that she loves him as a daughter should, he flies into a rage and disowns her. He goes into a similar rage against Kent for trying to tell the truth and banishes him from the kingdom.
The two older sisters turn on their father rapidly as soon as they have the kingdom in their hands. Their words have been nothing but empty, as King Lear learns too late—but he should have seen from the start. As his Fool tells him, the king is the biggest fool of all.