I just beat Halo Reach on Legendary with 2 for 275G (Campaign/Alone). I didn't jump for joy... I didn't make much noise. I probably smiled and made a quiet hurrah. The same spots that were a pain in the brain on Heroic were in some respects worse on the approach yet I made it all the way to the hand off of the Package before I saved/stopped for two days. Then today after playing Quantum of Solace for a few hours I went back to the final portion of the Pillar of Autum on Legendary.
I 'died' numerous times in and around the door way to the area before the MAC cannon. I killed the Grunts only to be blasted by the Zealot Elites. Those guys are insanely fast on Legendary though by hiding behind things I noticed they couldn't see me. So twice I lured one into the area near the stairs and snuck up behind him.
Assassinated two of the four just like that... not at the same time obviously. One on the right side of the lower floor and the other on the left side. The third didn't follow suit... so I had to try to sneak up on him... didn't work... still I kept melee up and almost lost all my health. Now I got a Checkpoint repeatedly during this dance with the four Zealots.
So the third is down and oddly the fourth with Fuel Rod Gun is facing away from me so I go straight up behind him... and Assassinate him too... I was like... I died at least 10 or 12 times trying to get up here... then I take all four in the space of ten minutes.
Of course the last challenge stood upstairs... the MAC.
I knew the approach patterns of the Phantoms so I tried blasting them when they about to fire or I was still too far away for them to shoot. Of course it worked and then I got a checkpoint on the MAC itself. I died a few times on the gun though in less time than it took me to beat Heroic at that spot... I wiped out enough airborne targets to get the target marker for the Cruiser overhead... so powered up... fired... then it was over.
Patience and Planning...got me through what I thought would be the hardest part of playing Legendary.