The phrase "as the clearest proof" is correct and usable in written English.
It can be used when you want to emphasize that something serves as the most obvious or undeniable evidence of a point or argument.
Example: "The results of the experiment, as the clearest proof, demonstrate the effectiveness of the new drug."
Alternatives: "as the most evident proof" or "as the strongest evidence".
The Attorney-General referred at some length to the consequences to the government should the decision be against it, and cited the debates in Congress on the passage of the act of 1862 as furnishing the clearest proof of the purpose of that body to require the immediate repayment by the company of the interest advanced by the government.
The clearest proof of his achievement may be that, as overpowering as his performance is, it never overshadows the rest of the cast.
As President Obama said on Tuesday night, "Today is the clearest proof yet that, against the odds, ordinary Americans can overcome powerful interests".
This cleansing gel is the first step in the Clear Proof Acne System.
While Mr. Zadroga's family and colleagues saw the autopsy report as clear proof connecting his death to the dust at the World Trade Center site, experts were troubled because certain specialized tests that might have identified material found in the detective's lungs had not been performed.
In an interview, Ms. Weingarten said she does not interpret Mr. Bloomberg's comments as an expression of his desire to make eliminating the Board of Education his main priority before moving on to other matters, but as clear proof that the mayor has linked the two issues.
On the plus side, Nick Clegg will be able to cite this as clear proof that the Lib Dems have not become a pale-blue offshoot of the Conservative party.
But with its emphasis on one sentence – without enough context – and its presentation on the front page, it comes off as clear proof of racial profiling in the New York Police Department.
