Almost. Prince Zill'us-Sultan actively persecuted Bahá'ís, instigated the martyrdom of at least one, and almost beat his wife to death. However, after having lost his position, finding himself in exile, he met Abdu'l-Bahá, and showed strong remorse. Abdu'l-Bahá asked him to send his sons to him, to be taught about the Faith. Two of them then joined the Faith.
Maybe Mírzá Abu'l-Faḍl-i-Gulpáygán?? He wasn't an enemy of the Baha'i Faith in the sense of Saul was to Christendom, as in he wasn't involved in active persecution or suppression, though he was an Islamic scholar who was opposed to the Faith theologically who was eventually convinced when a specific prophecy of Baha'u'llah came to pass that he thought was unlikely to occur.