The correct option is D annulled
The word 'ratified' refers to making something officially valid.
Option A, set aside refers to reserving something for a particular purpose.
Option B, unsettled refers to something that is not yet resolved.
Option C, destroyed refers to ending the existence of something by damaging or attacking it.
Option D, annulled refers to declaring something invalid.
Thus, according to the meaning, the word 'annulled' is the opposite of the word 'ratified'.