Also, can I just add that canonically Vincent had no qualms whatsoever about killing Lucretia's son. No "I hate to do this, but I know it has to be done" line.
By the way I know this topic is dead but I feel it should be pointed out that Vincent does address this. On the way to the final battle with Sephiroth, if you talk to him on the Highwind, he says, "Defeat Sephiroth... Defeat the son of that beloved woman... Am I on the verge of committing another sin......? Or am I atoning as best I can for only watching...?"
Because I was reminded of this line and thought of this thread.