Betrayal, murderous ambition, and general cruelty aside, Edmund has some reason to feel slighted in King Lear. The bastard son of Gloucester is constantly playing second fiddle to his "legitimate" brother Edgar and is unable to keep his anger to himself for very long. In Act 1, Scene 2, he airs his grievances to the audience in a soliloquy that makes use of alliteration:
Wherefore should I
Stand in the plague of custom, and permit
The curiosity of nations to deprive me
For that I am some twelve or fourteen moonshines
Lag of a brother? why "bastard"? Wherefore "base,"
When my dimensions are as well compact,
My mind as generous and my shape as true
As honest madam's issue? Why brand they us
With "base," with "baseness," "bastardy," "base,"
As Edmund finally makes his feelings known, he uses heavy alliteration of the /b/ consonant. The repetition of the sound gives a particular percussive force to his anguish and propels Edgar through the soliloquy; one can imagine an actor flinging these insults from his mouth in a live production of King Lear, underscoring the affront that the character feels at his constant dismissal for a quality entirely outside of his own control.