Roberta Tovey (Earth-33⅓)

Roberta Tovey was mentioned by Dr. Who as the most evil foe he had encountered over the years. (NOTVALID: Doctor Who? 95)

She placed a classified ad in the Gallifrey Gazette looking for any sign of her Grandfather (who "answered to 'Van Helsing'") around the time of the First Doctor's flight from Gallifrey in a stolen timeship. (NOTVALID: TARDIS Stolen!)

She was later recorded as one of the enemies whose defeat the Sixth Doctor had on his score card. He cited her to Mel, alongside many monsters and evildoers, as one of the foes he had decisively defeated, which meant the universe was now completely and forever safe. (NOTVALID: The Final Script)

Behind the scenes

 * In real life, Roberta Tovey was part of the main cast of Dr. Who and the Daleks and Daleks' Invasion Earth 2150 A.D., the two theatrical motion pictures featuring Peter Cushing as an explicitly human Doctor. The in-universe Tovey's status as an enemy of the Doctor is obviously a reference to the films' unpopularity in traditional Doctor Who fandom.