Ok I just watched the first movie.....the end assassin's name is Picot, who is played by Denis Braccini, who is not credited in the second film. In fact, there isn't even a Picot in the 2nd film. I could have sworn the fight scene in Supremacy is at his apartment and that's the same assassin. He's definitely a Treadstone agent I think because if you remember near the beginning, they contact all the Treadstone agents to hunt down Bourne.