Depends what you're doing with it... You can make any language you want slower than another language by using it badly

This is like saying that no car is faster than any other because it depends what gear you drive it in

True, but also a tautology.

Instead, I'd say that Rust & C are close enough, speed-wise, that (1) which one is faster will depend on small details of the particular use case, or (2) the speed difference will matter less than other language considerations.