An intelligent man is lost if he does not add strength of character to his intelligence.

[Un homme d’esprit est perdu, s’il ne joint pas à l’esprit l’énergie de caractère.]

Nicolas Chamfort (1741-1794) French writer, epigrammist (b. Nicolas-Sébastien Roch)

Products of Perfected Civilization [Produits de la Civilisation Perfectionée], Part 1 “Maxims and Thoughts [Maximes et Pensées],” ch. 4, ¶ 277 (1795) [tr. Mathers (1926)]
    (Source)

(Source (French)). Alternate translations:

A person of intellect, without energy added to it, is a failure.
[Source (1893)]

A man of wit is lost, if to his wit he does not join energy of character.
[tr. Hutchinson (1902)]

A man of intelligence is lost if his intelligence is not combined with energy of character.
[tr. Merwin (1969)]

A man of intellect is lost if he does not ally strength of mind to strength of character.
[tr. Pearson (1973)]

Any intelligent man who lacks character is lost.
[tr. Parmée (2003), ¶ 173]

A man with spirit is lost if he doesn't add to his intelligence an energetic character.
[tr. Sinicalchi]