I think it's pretty clear that "lightest" means "lightest"; the closest appropriate definition I can find in Merriam-Webster is "exerting a minimum of force or pressure." So I take it to mean "who can hit the lightest" means "who can hit with the least force."
Then propose an alternate definition and a creature that fits by that definition and also still fits the big scenes. As far as I can tell right now, you're just asking people to think about the possibilities of alternate definitions, explanations, and meanings, but not actually trying to use them to get to an answer. Are you trying to determine what the MitD is most likely to be, or are you just trying to have a discussion about how you think many things are widely open to interpretation?
Your analysis ignores everything about the MitD's well-demonstrated personality and other personal traits. You can look to the mechanics for whether MitD is capable of the actions he performs, but unless you think all members of a species have the same personality and that personality is in their stat blocks, this argument just doesn't wash. (Even less so in a story where the author has been very explicit about his belief in, and the themes of the story of, not judging a sapient creature merely by their race.)
But, again, you are still not actually trying to propose something that fits-- the Hunting Horror doesn't-- you are just trying to tear down the Protean. As I already said:
If the things you're talking about aren't in service of trying to find a better fit for MitD's species, then what is your goal here?
I can think of at least five people off the top of my head you have misquoted, mis-paraphrased, and thus mis-assigned opinions to that aren't theirs-- and in some cases you have insisted you were correct to do so, or that you have some rule against looking up what they actually said and therefore your paraphrasing should be good enough.
How often does that have to happen before you start to consider that it's you, not them?
(Indeed, considering your complaints that "the Protean has ruined the thread"-- even setting aside your presumption of speaking for many other people there-- have you considered that the only reason we're discussing the Protean today is because you brought it up?)
I'll second this.
Well, now, I'm appalled that you don't find keeping spreadsheets of your hobbies fun.
(Admittedly, I'm the kind of person who, after our Excel training on formulas and such at my job, thought, "Cool, I can use this to automate the breakdowns of my poker results in so many ways!")