Halo: Spartan Assault

This achievement is cumulative between both the Single Player and Co-Op Modes. Chances are, even after you have finished every Co-Op achievement and a majority of the Single Player achievements, you will still not have this achievement. Despite this annoyance, do not be afraid to actually spend your Spartan Points on weapons, boosters, or armor abilities in the pre-game lobby of each mission, as subtracting points from your total does not harm the achievement progress.

There is a simple way to grind this achievement out that involves very little skill and does not take anymore than thirty minutes – although you will not even have to grind that long if you are using this method post game after you’ve already obtained some thousand-odd points.

Basically, load up Operation A, Mission 1. You will want to turn on both the Black Eye and Hollow skulls, because these will give you a 4.5x Multiplier to your overall score at the end of the mission. Once the missions starts, simply proceed to eliminate all the enemies that spawn. There are just about twenty-nine Covenant forces to kill, and once you know where they all spawn, this mission should literally take one minute and fifteen seconds to complete. By the end of the match, you should be gaining around 900XP.

If you are using this method right off the bat, then simply do this anywhere from twenty-five to thirty times and the achievement will unlock. As stated above, that would only take you thirty minutes tops. If you are using this method after finishing all the Single Player and Co-Op missions, you’ll unlock the achievement sooner.

While 25,000 XP may seem like quite a daunting task, it should eventually come as you repeat missions to get more stars and complete challenges (which also give XP). You may also want to use a skull or two, depending on how confident you are at the game (I played most of the levels with at least Hollow on).