This question will be filled with spoilers.
Despite having played a perfect paragon playthrough, I was unable to select the third paragon dialog choice in the final confrontation with the illusive man. It said something like "but you already have".
I had to choose a normal option, which led to a renegade interrupt that I took, shooting and killing him, but saving Anderson (for a little while at least)
What would've happened if I chose it? Would I have convinced him?