Aubin Tabor

Aubin Tabor was a Federation ambassador ostensibly assigned to help convince the Chiarosians to join the Federation instead of the Romulan Star Empire. In fact, he was a Section 31 agent whose mission was to help make sure that the people of Chiaros voted to join the Romulans. Upon reaching Chiaros, Tabor was killed in the first diplomatic meeting. (TNG novel: Section 31: Rogue)