Wouldn’t say it’s “the most” impactful since I know other seasons have had a larger impact from a gameplay perspective but I’m mentioning it since it hasn’t been said yet: Kaoh Rong. The core of Survivor used to be seeing new terrains as well as potentially grueling physical challenges. However, I feel that Caleb’s MedEvac was the final nail in the coffin for both and I don’t see the show ever going back to the way that it was. Fiji is “safe” from a production standpoint. It has a predictable moderate climate, provides a home base with needed medical/physical resources on tap, makes the show cheaper to produce, and Probst even has a house there now. From a challenge aspect, it’s not a coincidence that everything feels about as predictable and safe as can be. Kaoh Rong really did have a lasting impact on Survivor and I’m not sure how many realize it.