Good Morning,
Just wanted to say that the achievement for completing Halo 5 on Legendary solo is bugged. I completed the campaign last night and didn’t receive the achievement. I’ve power cycled my Xbox One twice with no results. Is there anything I can do to unlock it?
Your service record doesn’t show a time completion for Guardians. Try playing that mission again and see if the achievement pops.
Ugh, so many deaths… and hours… 
Why would my service record say 15/15 completed Legendary but since there isn’t a time recorded I didn’t the achievement… that’s a little confusing…?
Update: The achievements unlocked randomly. I left my TV idling at the Halo Wars: Definitive Edition screen and the achievements popped. Not sure what caused it to pop. If you guys need any info to help hammer down a reason I’ll be happy to share.