5. Peri Brown (Mindwarp)
Nicola Bryant's Peri Brown appeared with the fifth and sixth version of the Doctors, meeting her apparent demise during the season long Trial of a Timelord serial. She was a controversial character criticism was leveled at how she dressed, and producer John Nathan-Turner admittrf that the character was created to bring some sex appeal to the show. She departed in the second adventure of the Trial season, entitled Mindwarp. Through a very confusing a double-crossing, twisty episode, Peri eventually has her head shaved and the mind of Kiv placed in her body. Possessed by the alien, she is then shot and killed. The Doctor meanwhile was drawn to the TARDIS and back to Gallifrey before he could reach Peri to prevent the mind transfer from going ahead. It was a shocking conclusion for such a well-known character. So shocking in fact, that they ended up slight retconning it. Later in the Trial season in The Ultimate Foe, it was explained that her death was faked by the Valeyard, and instead she ends up marrying Brian Blessed's King Yrcanos. Now, I like Brian Blessed. But the choice between spending every waking moment with him or death is a hard one, and not a fate I'd foist on anyone.