Ben 10 Galactic Racing

You want to go into Showdown mode from the menu for this one. Pick the Ultimate Alienation gametype and set the time to 1 minute. You need to win 10 of these and your job is to "frag" the most kart racers. You can make this extremely easy and effortless by just standing on a power-up and holding the left analog stick upwards and keep pressing "A". It doesn't really matter which track you choose, I went with Asteroid Arena.