Is C the fastest language because most kernels are written in C viz. Unix, DOS and Macintosh?

Hypothetically if there were an OS named YAOS(yet another OS) written in ALWAC (Another language with another compiler), assuming ALWAC is assembly optimized of course. Would ALWAC be comparable to C in performance, given that C is the fastest language that there is.

To rephrase the question: Would it be a good idea to write a language specifically for a kernel plugin like Symbian OS, Purity OS or Nutanix OS to speed up the development without compromising C like performance? A language native to an OS/kernel module, if you will. I mean, C came after Unix, historically, which is what raised this doubt.