Bakugan: Defenders of the Core

Before getting started in Duel Mode, you can change the Battle Arena CPU to "Easy" and number of rounds to 1. This will shorten the amount of time it takes to beat the CPU five times. If you need to, you can also increase your health to 150% and decrease the CPU to 50%. Plus, you can choose a Bakugan for yourself and your opponent that gives you the superior type advantage. With all these perks, it should be easy. After you win, hit Retry and do it four more times.