I hope anyone who put themselves through this ordeal posts in this topic, because you’re the kind of person I either have the utmost respect for or the person I fear the most. Either way, I want nothing to do with you and posting in here helps me with that.
I didn’t get past level 3. The prometheans teleporting around one-shotting me with melee attacks far outside the reasonable range was something I was willing to put up with for an hour or so thinking “hey, this is legendary, it shouldn’t be easy”. But an hour later when I’m still getting killed from a range so far that a suppressor still needs to be burst fired to even hit a damn thing, I give up. There’s difficult, and then there’s “we don’t give a rat’s hairy -Yoink-, don’t bother playing legendary because we sure didn’t playtest it” difficult. Call me a noob, or a scrub, or whatever the word de jure may be in regards to somebody lacking in skill; I won’t defend myself because I refuse to put myself through this garbage, contrived, totally ridiculous difficulty anymore. I don’t hate myself quite that much. In fact, anyone who did finish legendary in this game should be immediately referred to a psychologist if not asylum, because clearly they’re one step away from suicide.
In conclusion, this topic serves absolutely no purpose besides humbling my ego even further after coming to the conclusion that I’m not going to surpass the AI on this one. Laugh if you want, cry if you want, do whatever the hell you want. I’m out of here.
Legendary can be tough OP, I rememeber having a hard time doing Long Night of Solace on Reach and Cortana in Halo 3 kicked the crap out of me for days and days. If you don’t mind using guides, I’d recommend trying some of the tips and tricks that Mythic Tyrant uses in his Legendary guides. Or if you’re up for a little more speedrunning type action, Naked Eli has some great tips and skips you can use 
That section is definitely very rough. What I did was, I turned the Mythic and Tilt skulls on for extra durability (and of course Catch for fighting Knights) and used Tyrant’s MYTHIC guide (not Legendary) to run past everything. There’s only one Knight in the entire mission you absolutely, positively HAVE to kill and that’s the first one. His health is so astronomically high with Mythic and Tilt on that the only way to kill him is with the “backsmack” i.e. get behind him while he’s chucking nades and assassinate him.
There’s a glitch you can use to completely bypass the second set of three shield generators, that involves flying the Banshee past an invisible wall and clipping into the tower. That’s in the video as well.
Trust me I’m the world’s worst Halo player LOL but I beat 4 on Legendary on my 360’s offline profile (not in my service record, you’ll just have to believe me). You can do it! Take some time off to cool down before attempting it again. I spedran past most of Forerunner, Reclaimer and Shutdown using walkthroughs. Dawn, Requiem and Composer were actually kind of fun to slug through, to me. (Not coincidentally, those are Covenant-only levels with no Prometheans.) Infinity and Midnight were the absolute toughest missions to me. You can skip some groups of enemies in those but others you gotta kill. Use every shot of Incineration Cannon ammo you can find for Midnight.
Are you talking about Legendary or LASO? I feel like Halo 4 is the easiest of all the Halos to solo on Legendary. In case you didn’t know plasma pistols still take a knight down to no shields and only requires 3-4 light rifle headshots to down.
I hope you stick with it, grab someone else on the recruiting section of the forums if you need to.
Reach imo was the worst, but yeah 4 was a pain too. Gotta get dem chievo’s dough
i got passed halo 4 legendary in one night. I finished in one night because i have a system. the system is have one fully auto weapon and one semi auto weapon, shotguns, rocket launchers, rail guns, all replace fully auto weapons.