Best female villains.

Ditto Judy Parfitt, the best guest actress to grace the show, has a great spotlight episode with "Bullseye" and shines in "White Elephant", too: sadly she's given a generic, nearly mute henchwoman role in her following appearance and has to share her duties with her fellow villains way too much in her final one (not to mention that the confused plot doesn't hold any interest and her demise is rather unmemorable).

Julia Arnall is a memorably icy and ruthless villainess in "Intercrime": I think she might have made a fine recurring baddie and nemesis for Cathy. The organization itself returns in a Tara King episode: possibly the worst in the entire series, though.

For a nice supporting villainess, Lois Maxwell is quite memorable as the machine gun-wielding nun in "The Little Wonders", who also punishes the villainous bishops by taking their "toys" away when they behave childishly.

Janine Gray was appropriately creepy as the first Ola in "Don't Look Behind You": much better than the insufferably hammy one in "The Joker".

From the Peel era, I thought Yolande Turner's Receptionist deserved to be in a better episode than "The Girl From Auntie" (as Alfred Burke's Auntie did). She has a great, natural bad girl quality about her. Her demise (her head getting stuck in the cage's bars) was quite embarrassing, though.