According to Preterists did "the man of sin" (2 Thessalonians 2:3) become manifest before 70AD? If so, who was it? KJV 2Th 2:1  Now we beseech you, brethren, by the coming of our Lord
  Jesus Christ, and by our gathering together unto him,  2Th 2:2  That
  ye be not soon shaken in mind, or be troubled, neither by spirit, nor
  by word, nor by letter as from us, as that the day of Christ is at
  hand.  2Th 2:3  Let no man deceive you by any means: for that day
  shall not come, except there come a falling away first, and that man
  of sin be revealed, the son of perdition;  2Th 2:4  Who opposeth and
  exalteth himself above all that is called God, or that is worshipped;
  so that he as God sitteth in the temple of God, shewing himself that
  he is God.  2Th 2:5  Remember ye not, that, when I was yet with you,
  I told you these things?  2Th 2:6  And now ye know what withholdeth
  that he might be revealed in his time.  2Th 2:7  For the mystery of
  iniquity doth already work: only he who now letteth will let, until
  he be taken out of the way.  2Th 2:8  And then shall that Wicked be
  revealed, whom the Lord shall consume with the spirit of his mouth,
  and shall destroy with the brightness of his coming:  2Th 2:9  Even
  him, whose coming is after the working of Satan with all power and
  signs and lying wonders,  2Th 2:10  And with all deceivableness of
  unrighteousness in them that perish; because they received not the
  love of the truth, that they might be saved.
The Preterist Archive gives this answer, among others.


  The best answer - we believe - is that it was both an office (the "what") and a person (the "one who" or "he").  More specifically, it was the institution of the Jewish priesthood led by Ananus, the high priest.


What About Paul's Man of Sin? - Preterist Archive

They also say:


  Josephus also records that before this John of Gischala, the son of Levi, was established as the Zealot leader in control of the Temple area (there were three Zealot factions), the power of Satan was already doing his deceitful and treacherous work. 


Wikipedia notes that John 17:12 also uses the term "son of perdition," referring to Judas. It also gives this information.


  Some scholars[3] and theologians[4] down through history, including Hippolytus,[5] Luther,[6] Wesley,[7] Manton,[8] Schaff,[9] et al, say that first "Son of Perdition" reference is to Antiochus IV Epiphanes, the man who attacked the Second Temple in Jerusalem and defiled it by sacrificing a pig on the altar, erecting a statue of Zeus as himself in the temple, raiding the Temple treasury and minting coins saying "Theos Epiphanes" (God manifest), etc. Even those theologians who advocate an interpretation of Daniel that includes the Roman Empire in their analysis recognize Antiochus as a prototype.[10]


Son of perdition