This one is simple. You need to complete the following:
All training missions
All Battle missions
All Hero battles
All Survival missions
It's a bit of a grind but won't take you too long.
Difficulty is irrelevant, play on normal if you want this trophy quickly.
Stars are irrelevant, it doesn't matter how many you come out with as long as you complete the mission.
Collectibles are irrelevant, it doesn't matter if you collect them all or none at all.