that scene in tlo where thalia tells percy he can't start feeling sorry for luke bc luke made his choices. and thalia reveals that the reason they couldn't make it to camp in time for all of them to make it to camp was bc luke kept picking fights. and annabeth never saw this as wrong bc luke was her hero. so thalia had to pick up the pieces. and percy thinking both that luke was put in a cruel position and that luke was putting others in a cruel position. and percy is the only character who understood both sides of luke bc annabeth sees only the best of him and thalia sees only the worst. and that's why percy is the prophecy kid and the one who gives luke the knife. bc annabeth had spent the entire series essentially giving luke the knife when he didn't deserve it. and thalia was never going to give luke the knife. but percy is the only one who can see exactly when luke deserves the knife.