Nine Orions and one Hecate confirmed, more possible. At least two were destroyed by the Colossus, the NTD Repulse and the NTD Andronicus. The Colossus also possibly destroyed the Vasa, but we only know that it was destroyed, not by whom, at the Gamma Draconis node.
The Colossus also destroyed (with player help, among others), the NTC Majestic, NTC Refute, NTC Conquest, NTC Camisard, NTC Vanguard, NTCv Hawkwood, NTCv Congreve, and NTCv Danton.
That's just the ships in the NTF it destroyed. Adding in Shivans, you get the SJ Sathanas, the SD Beast, of the major Shivan captial ships. We have no idea how many smaller ships the Colossus destroyed before Their Finest Hour.