telling the world of iraq s weapons of mass destruction. the gravity of this moment is matched by the gravity of the threat that iraq s weapons of mass destruction pose to the world. reporter: those weapons did not exist. the intelligence was flawed. telling abc s barbara walters he felt terrible about the claims made in that speech. do you think this blot on your record will stay with you for the rest of your life? of course it will. well, it s a of course it will. it s a blot. i m the one who presented it on behalf of the united nations, united states to the world and it will always be part of my record. how painful is that? it was painful. it s painful now. reporter: tonight, former president george w. bush calling powell a great public servant. bill and hillary clinton saying he was a courageous soldier, a skilled commander, a dedicated diplomat and a good and decent man. president obama saying he