Since the 18th century, the meaning of "awful" has weakened to that of a negative intensifier; we say such things as: "You've been an awful time" and "I'm an awful duffer." As an adverb, especially in American English, it can even be positive, as in: "That dinner was awful good." In Shakespeare, it was used only in its original Anglo-Saxon sense of "awe-inspiring, worthy of respect". In Pericles, Gower describes Pericles as a "benign lord That will prove awful both in deed and word" (II.Chorus.4). This meaning is easy to spot when awful goes with words denoting power, such as sceptre, rule and bench (of justice). It is a little more distracting when we see it used with general words, as when one of the outlaws in The Two Gentlemen of Verona tells Valentine that they have been "Thrust from the company of awful men" (IV.i.46).
David Crystal is author, with Ben Crystal, of Shakespeare's Words, published by Penguin