I just competed the halo 2 legendary campaign parlay earlier but did not unlock the achievement for completing the game on legendary. It actually says 92% completed. And ideas for fix or just wait it out. Or do I have to complete it again?
I’m not sure. I also just completed the Halo 2 legendary playlist on solo, it all went fine for me.
I fear you might have to replay the level which didn’t say complete.