The lights are on
So, as a lot of people try to complete halo 4's campaign on legendary difficulty, many give up because of the difficulty and sometimes frustration with the game. So here's and easier way to complete the campaign in legendary. First what you want to do is go to the first mission (prologue) and select legendary. Since this mission is basically a video you don't do anything and this can also be done with the epilogue (last mission). But for the other missions, beat them on easy, then what you want to do is when you have all of those done on easy, select one of the missions you did on easy and select the last rally point (example: rally point delta may be the last rally point in a mission), so select the last rally point and select the legendary difficulty, complete that rally point on legendary and in the top right if the screen a box will pop up and it looks like the box when you complete a challenge, it will say "name if mission" complete, 0 xp. And that's when you've completed the mission on legendary. But you can just go to the next mission, when the next mission does start, exit out and repeat this process, select the last rally point of the next mission with legendary difficulty. And complete that and the challenge comets box will come up with the name of the mission complete, 0 xp. And when all missions are successfully completed on legendary using this process, all armour, gamer points, achievements, etc will be rewarded. Hope all of you halo 4 players find this as helpful as i did.