This one is a bit weird. Go to quick race, set the AI to Exhibition, race type to Magnet Mayhem and choose a nice long track. Start it up and what you have to do is destroy all opponents before the last 2 laps and to do this I advice to stay in front of all the opponents and fire backwards and maintain your speed, also when you are gonna unleash the magnets make sure you have a full bag. When you are own your last lap it should come up. Doing this will also net you Destructor, Destructor II, 600 combat points and 1000 combat points.