For once, Charles seems to be asserting his power over Edmund. He knows that he’s more powerful here at the top of the castle (as evidenced by Edmund’s obvious fear of heights). And yet Charles’s consuming sense of power is tempered by his realization that, eventually, he’ll have to go back to Warings, where Edmund will bully him. Charles gives up too easily. He lacks Edmund’s reckless confidence and sense of superiority, and that’s why Edmund is able to intimidate him.