In Less Than Nothing, Slavoj Žižek addresses the process of “negation of the negation” in Hegel’s dialectical process, with a lucid example with regard to the state:
To illustrate this very procedure […], let us note how the Marxist critique of “bourgeois” freedom and equality provides a perfect case of such a pleroma (fulfillment of the law): if we remain at the level of merely legal equality and freedom, this has consequences which lead to the immanent self-negation of freedom and equality (the un-freedom and inequality of the exploited workers who “freely” sell their labor-power on the market); the abstract legal principle of freedom and equality has thus to be supplemented by a social organization of production which will no longer allow for the self-undermining of the principle in its very enactment. The principle of freedom and equality is thereby “sublated”: negated, but in such a way that it is maintained at a higher level (293).
For me, this was certainly a much-needed example of negation in a dialectical movement. Another example brought up several times by Žižek and Hegel is the history of the French Revolution.