The phrase "一无是处" is formed conceptually by combining the idea of absolute negation ("一无", meaning "not a single one" or "completely without") with the notion of a correct or valuable point ("是处", meaning "a right place" or "a merit"). It builds its meaning by painting a stark image: if in every single place or aspect one looks, there is not one that is correct or good, then the entire subject is deemed to have no merit whatsoever. This creates a powerful, holistic judgment of total worthlessness through the simple, absolute logic of universal negation.