Just completed this last night but cheevo did not pop. Got the speedrunning one instead but some parts reverted to normal without any reason. Tried to reload on existing file and continued. When I got to the 4 spires, game loaded on legendary but without skulls active. Wtf! Reloaded save file at that point again and completed campaign. Can’t even go back to see what levels didn’t complete…such a joke. Please implement another hot patch.
Anyone else have issues with this one?
Did you use the invincible glitch?
I guess activating skulls later does not work correctly. My tracker didn’t raise After i started the game on easy and turned on everything later…
No glitch was used except for the Scorpian Tank gun if that counts. Others have breezed thru with it though. I started on Legendary all 12 skulls; did not know you could switch difficulty and never did (intentionally). Hoping it pops after a bit after I log on again.
Sorry to hear that bro. I’ve had a number of other less significant achievements not pop for me either. Typical 343 -Yoink!- job.
I did find continuing a save set my rank or skulls differently. I had better luck loading the save rather than pressing continue.
The problem is that every time you press continue the skulls reset… This is the bug u will get teh achievement only when you ALWAYS load gamesave and don’t press continue so the skulls stay on 
leard this the hard way