Empire era Star Wars. Expanded canon allowed for both sides.

1: Covenant vs. Empire ground battles. Infantry vs. Infrantry. Vehicles vs. Vehicles.

2: The Covenant attempt to invade Coruscant. Reach scale invasion effort.

3: The Forerunners at their peak have to conquer the entire Star Wars universe.

BONUS: Chief and arbiter armed with energy swords and plasma pistols vs the various Darths. One Darth at a time, weakest to strongest, gauntlet style.

DOUBLE BONUS: The Didact vs the various Darths/Jedi. Also gauntlet style.