Re: Khan the most dangerous enemy of the original crew?
I suppose it could be interpreted as really meaning most dangerous for the crew, rather than in general. Which would still be debatable. But he was the only one who ever succeeded in actually killing a main character...
That explains why Khan is the most dangerous villain to fans, but there are no main characters from Spock's point of view. In universe Spock is no more important than Red Shirt #554.
"Who are you?! And how did you get in here?!"
"I'm the locksmith. And... I'm the locksmith."