This is an easy achievement. You just have to win a local offline World Tournament. That´s the only requirement to get this achievement. My first advise would be to set the game to just 4 fighters, and set the difficulty to easy. Then, make a personalized character as stronger as you can. You will win in no time.
If you have any trouble, this map is the biggest of the game, so just press LT+LB to use a Super Rise, and once you get to the upper area, charge fully. Press A+A two times to fly fastly to your opponent´s back and use your ultimate. Battles shouldn´t last long.
You will get the achievement after beating the last opponent and getting the WINNER text on the battler´s board (you have to wait a little).