At the very beginning of his book Negative Dialectics, Adorno writes
As early as Plato, dialectics meant to achieve something positive by means of negation; the thought figure of a “negation of negation” later became the succinct term. This book seeks to free dialectics from such affirmative traits without reducing its determinacy. The unfoldment of the paradoxical title is one of its aims.
Can the (ultimate) difference between negative dialectics and Plato's dialectic, be (succinctly) paraphrased?
Specifically, in what way does ND not achieve something positive?