Stage character who says "How sharper than a serpent's tooth it is / To have a thankless child!"

LEAR

This tragic king divides his kingdom among his daughters but is betrayed by two, leading to his eventual madness on a stormy heath.

This clue quotes a famous line from Shakespeare’s King Lear, where the aging king laments his daughter’s betrayal. The speaker is Lear himself, making the answer his name—no wordplay, just a direct reference to the character. If you know the play, the bitter tone of the line gives it away.