I'm someone who thinks "That Which Survives" deserves its bad rep. I would rate it bottom 5 TOS for many reasons. Mostly because Kirk and Spock act like jerks. It has good moments but after seeing it I just want to punch Spock in the nose and give Kirk the finger (if I did that sort of thing). I also find the composition of that landing party difficult to understand. Apparently this planet was an amazing unihabited scientific marvel, so who do you beam down? Chief science officer and a bunch of scientists? No Captain, Helmsman and one scientist. However surprise surprise it all worked out. Best landing party ever except for the scientist but hey he wasn't a regular. Kirk and Sulu were probably in retrospect excellent choices but how did Kirk know?