6. Sixth Doctor - The Twin Dilemma (1984)
Colin Baker had a rough time in his role as the Sixth Doctor. Originally intending to give Doctor Who a stronger level of realism, it instead caused outrage for the amount of violence in the series and the dark nature of its storylines, but because of this though, in hindsight many of the stories from this era are ranked amongst the best ever. Not so with the Twin Dilemma, however. Coming hot off the heels of Peter Davison's final episode The Caves of Androzani, which was a roller coaster of intense action and powerful drama, we got Colin Baker's debut story, which offered.... nothing. It's hard to explain everything that makes this serial a turkey. It features the Doctor suffering through post-regeneration trauma and assaulting his companion Peri, a pointless plot that never explains all the questions it raises, and a giant talking slug with fur. Let's suffice it to say it was ranked as the worst Doctor Who story ever in a poll conducted in 2009. Fortunately, soon after this the crew got themselves together and gave Colin Baker some awesome stories like he deserved.
If You'd Like a Good Colin Baker Story: Vengeance on Varos, an exploration of violence and brutality in television; there's his sole Dalek story Revelation of the Daleks, usually considered one of the best ever serials with them; or the amazing Trial of a Time Lord, another full season story.