Bakugan: Defenders of the Core

Simply finishing the Story Mode will gradually unlock every Bakugan in the game except for one. The last one is Maxus Helios, the strongest Vexos Bakugan. To get Maxus Helios, start a new Story Mode after beating the game. In the exploration mode before some missions, make sure to get every unopened chest. Some of them will contain Bakugan Traps. When you collect the last Trap, Maxus Helios is unlocked along with the trophy.