Par score: 16,000
Recommended difficulty: Legendary
This one isn't as hard as it may seem. Use the Spartan Laser to take out the Wraiths at the start for some easy points, and keep a streak up for maximum points throughout the rest of the level. Here's a video guide:
This video guide is for Legendary with Famine, Mythic, Thunderstorm and Tough Luck enabled. The skulls are not entirely necessary but make earning the required number of points much faster.