OK, apparently I can't complete any freaking challenge. I'm trying to do the 2nd one where you have to kill 15 using slow motion. I'm doing that...what the hell else do I need to do?
If you go back to the main menu in the middle of a round, go to start a new round, go back to the main menu and continue your previous round, it'll reset the time but still start on the hole you left off. Easy way to get the hard badge.