The ‘One who restrains’ might have been the Emperor Claudius. When he was poisoned Vespasian became Emperor. Vespasian eventually appointed his son Titus to command the Roman legion that destroyed Jerusalem causing a million casualties. Christians were mostly already gone then. As Emperor Titus perpetrated a few sinful activities such as murder, although that was perhaps somewhat normal for most emperors. Suetonius reported that he had a “rapacious character” yet he was not nearly as bad as Nero. I believe II Thess. 2:6-7) fits rather well in partial preterist eschatological opinion. Of interest is footnote 1 to chapter 7 of Suetonius’ article on Titus that mentions ‘Berenice and her brother Agrippa paid a visit to Festus and were present when St. Paul answered his accusers’.
