Best answer is Balaji Vishwanath. As Sambhaji (1680-89) were succeeded by Rajaram, Shivaji II, Tarabai and Shahu ji. Balaji Vishwanath played a crucial role in the final victory of Shahu by winning over almost all the Maratha sardars to the side of Shahu. Under Baji Rao I, Maratha power reached a zenith, but that option is not given.