Axle City champion Achievement
Axle City champion100
Finish the AdventureAdventure Mode consists of three locations, each with a set of three races (which make up the three championships). To win a championship, you must finish in the top three in all three races of that location. Note that these races must be played consecutively (choosing 'Next Track' after each race); you can't choose each of the three races individually. You can play them all on Easy though. As for racers, I prefer Watts as she's fast and her special ability does double duty: it gives you a speed boost while also disabling any racers near you. Blaze and Zeg also have boost abilities too, making them good choices.
After you finish the first set of the three races, you'll unlock an achievement and the next set of three races. Once you've completed all three locations, you'll unlock the Final Adventure, which is a single race on a short track, five laps, against a single opponent. Again, this should be no problem. As soon as you start this final race, you'll unlock Awesome Adventure (100G), and when you win (you actually need to beat the other racer in this final race), you'll unlock this achievement.