6. Mercy Hartigan (Dervla Kirwan, The Next Doctor)
'The Next Doctor' has the unfortunate fate of being sandwiched between 'Journey's End' and 'Planet of the Dead,' meaning it often gets passed over. But the performances throughout the special are all gold-standard, from David Morrissey's Jackson Lake, to Velile Tshabalala's Rosita to of course, Dervla Kirwan's turn as the tragic villain Miss Mercy Hartigan. It's implied all the way throughout the episode that Hartigan was abused, perhaps sexually, as a child and young woman and this adds a great deal of sadness to the character. Constantly passed over because of her gender as an adult, this becomes a source of rage and frustration to Hartigan. Kirwan shows the rage, passion and intelligence of the character, especially in the incredible scene where she sidles up to a funeral in the snow in a bright red dress and slaughters the men there with her pet Cybermen. Hartigan's strong will is what allows her to overcome the reprogramming of the Cybermen and take control of the Cyberking rampaging through London, but Kirwan keeps it in check so she never comes across as some control-freak, iron-fisted cackling harpy; her character is present just as strongly on the ground talking to her enslaved men as it is hundreds of feet above London, strapped to a chair. Nice work, Kirwan. It's just a shame we seem to forget your episode actually happened.