Spock

Spock was a half-Vulcan, half-Terran officer in the Imperial Starfleet. He served as executive officer of the ISS Enterprise from 2265 to 2285, and later a cabinet minister under Emperor Tiberius. After the crossover incident of 2267, Spock formed a decades long plan to end the brutality of the Terran Empire.

Projecting that Kirk's ambition could carry him to the throne, Spock would conceal his own ambition and follow him to power, acting as an influence until he could take the throne. Spock would also find allies to help Kirk to power and prepare for his eventual downfall. This included Spock's mistress, Marlena Moreau.

However, Spock's plot was uncovered by Emperor Tiberius and he was executed for treason. Any reforms Spock began have long since been reversed.