It was Sierra 117 on H3 MCC. I did it solo and I did use halo completionist’s guide for some points throughout the mission (mainly that one section that pits you up against like 15 sniper jackals), though for some of the enemy encounters I used arbiter as a distraction while I punched shield jackals to get health. Gotta say it was kinda rewarding to deviate from the guide a bit and still have everything work out in the end.
At least its not like 2 where any tiny mistake can kill you (because F**k you its halo 2 legendary). In 3 theres still room for mistakes, but not too much.