5. The Daleks' Master Plan - All episodes except 2, 5 and 10
As you can see with this one, it's easier to list which episodes still survive than the ones that don't. A key reason is the sheer length of the story - at 12 episodes long, The Daleks' Master Plan is easily one of the longest Doctor Who stories in the show's history.
It's definitely the longest Dalek story ever made. At 12 episodes long - 13 if you include the prelude Mission to the Unknown - there's definitely a risk of the story dragging. Stories often drag at 6 episodes, let alone 12!
Fortunately, The Daleks' Master Plan packs in a lot. The TARDIS crew journey to so many times and places and face so many threats, as they're relentlessly chased across time and space by the Daleks. We also have a new team of villains aiding the Daleks, led by Mavic Chen - the "Guardian of the Solar System". The stakes feel high and there are a lot of shocking moments - not least of which is the first-ever death of a companion!
The Daleks' Master Plan is an incredibly ambitious story, and based on the surviving episodes as well as the soundtrack, it's a story that holds up surprisingly well. It would be amazing if we ever got the chance to watch the 12-part epic in full.