Mario Party: The Top 100 Master CPU mode
Collect all 300 Mini Stars in Mini Game Island by placing first in all 97 mini-games to unlock the Master CPU difficulty.
Hard Mini Game Island
Successfully complete Mini Game Island to unlock the Hard difficulty for it, which requires you to finish first in a mini-game to proceed.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art / Original