We betray more often through weakness than through deliberate intention to betray.

[L’on fait plus souvent des trahisons par foiblesse que par un dessein formé de trahir.]

François VI, duc de La Rochefoucauld (1613-1680) French epigrammatist, memoirist, noble

Réflexions ou sentences et maximes morales [Reflections; or Sentences and Moral Maxims], ¶120 (1665-1678) [tr. Tancock (1959)]
    (Source)

Present in the 1st edition (1665). The manuscript has a variant form:

La foiblesse fait commettre plus de trahisons que le véritable dessein de trahir.

[Weakness makes one commit more betrayals than the real intention to betray.]

(Source (French)). Alternate translations:

Weakness occasions the committing of more treacherous actions, than the real design of being treacherous.
[tr. Davies (1669), ¶178]

Treachery is oftner the Effect of Weakness, than of a fixed Design.
[tr. Stanhope (1694), ¶121]

Treachery is oftner the Effect of Weakness than of a form'd Design.
[tr. Stanhope (1706), ¶121]

Men are oftener treacherous through weakness than design.
[pub. Donaldson (1783), ¶425; ed. Lepoittevin-Lacroix (1797), ¶117]

Men are treacherous oftener through weakness than design.
[ed. Carvill (1835), ¶402]

Men are more often guilty of treachery from weakness of character than from any settled design to betray.
[ed. Gowens (1851), ¶123]

We often act treacherously more from weakness than from a fixed motive.
[tr. Bund/Friswell (1871), ¶120]

Deception is more often the fruit of weakness than of an intent to deceive.
[tr. Heard (1917), ¶120]

Treachery is the result of weakness more often than of a deliberate intention to betray.
[tr. Stevens (1939), ¶120]

Treason is more often the result of weakness than of a deliberate plan to betray.
[tr. FitzGibbon (1957), ¶120]

We are oftener treacherous through weakness than through calculation.
[tr. Kronenberger (1959), ¶120]

We betray more often from weakness than out of a resolute intention to betray.
[tr. Whichello (2016) ¶120]