I don't think he was "ruined" at all. I think, however, that being stuck in a harsh desert for fifteen years would drive anybody binky-bonkers....He was a much richer and more interesting character than that, at least until Harve Bennett and Jack Sowards ruined him by turning him into a cartoon.
But how much more interesting would it have been to see a Khan who hadn't gone mad, who still had the intelligence and cunning to use the power of Genesis to build a new empire and challenge the whole Federation, instead of just going after Kirrrrrrk and blowing himself up in the process? Or how much more interesting would it have been if we'd actually gotten to see what Khan and his people could've built in a hundred years?
I think you have your next Myriad Universes story
