I think he could beat Windu individually. His Force powers and TK can overwhelm him. Unless Windu is in the same state of mind he was in RotS when he faced Palps, I doubt he could defeat Revan 3.0 in an all-out. Even though I seriously question the notion of actually requiring Marr, Satele, your main character, Vizla, Theron and the Wookiee to take down Revan, it has to be taken into consideration when analysing his power and his abilities as a combatant. SWTOR certainly attempts to make Revan an uber powerhouse. Not sure if they entirely succeed, but he's probably a serious threat to the great majority of Sith or Jedi in the entire mythos in a battle.