9. Genesis Of The Daleks (1975)
This celebrated serial is more timey-wimey in its concept than in anything that actually happens, but it is so iconic that it deserves a place on this list.
The Doctor (Tom Baker) and his companions are tasked by the Time Lords to prevent the Daleks from ever existing, so a vision of the Time Lords in which the Daleks become the supreme power in the universe will never come to pass. Things take a turn when the Doctor’s future knowledge of all the ways the Daleks will be defeated falls into the hands of their creator Davros. The question is then not only will the Doctor fail in his mission, but has he actually made the situation worse.?
In the end, the Doctor is able to retrieve the data, but is too overwhelmed at the moral implications of his mission to deliver the final killing blow to his enemies.