The phrase "achievable only by" is correct and usable in written English.
It can be used to indicate that something can be accomplished exclusively through a specific means or method.
Example: "This level of expertise is achievable only by years of dedicated practice and study."
Alternatives: "attainable solely through" or "possible exclusively via".
If you thought italic writing was something achievable only by ctrl + I, this is the style for you.
It is a surprisingly difficult gesture to make, achievable only by using an odd combination of small muscles in the hand known as the lumbricals.
The man looks disappointed and barely thanks me; his partner, whose melancholy hauteur is achievable only by elegant Frenchwomen of a certain age, buries her nose in a magazine article called "The Voice of Hamas" and does not look up again.
Because the simultaneous control of characteristic impedance and phase shift in each of the constituent half-wave layers is not achievable only by layer-sizing, the varied layers must be realized by metamaterials.
As an emotion it is not simply a positive subjective state, as on some contemporary views, but an emotion that meets certain normative standards: "a state of non-contradictory joy a joy without penalty or guilt," achievable only by "the man who desires nothing but rational goals, seeks nothing but rational values and finds his joy in nothing but rational actions" (p. 32).
A successful strategy to develop tissue replacement is achievable only by adopting a multidisciplinary approach that combines the principles of engineering and the life sciences toward the development of biological, biofunctional tissue replacement substitutes that can either fully restore or improve tissue function.
Chess is not the only field where computers have achieved success formerly thought to be achievable only through human creativity.
The upper bound is achievable only for ideal channels, and the CLD approaches the upper bound by an amount proportional to the given channel quality.
The other emphasises a confidence achievable only with unconditional support.
It is probably achievable only with some significant restructuring of the management of central government procurement.
Currently, cure is achievable only in patients with localised disease.
