。
I won't let you find my weak point!
Literal
I [of-の] weakness [object-を] not-let-find [strong-emphasis-ぞ].
見つけさせない is the negative causative of 見つける ('to find'): causative 見つけさせる ('make/let find') + negative ない = 'not let find.' The causative-negative together expresses 'won't allow [you] to find.' The ending ぞ is a strong, masculine assertive particle — more assertive than よ, used for self-declarations or challenges.