I played through Outskirts on Legendary today and saved and quit at the end after reaching the end of the tunnel. However, I did not get credit for having completed this level in-game nor did I unlock the achievement. I came back a little while later and continued with and finished Metropolis. I know the game saved my progress because I started Metropolis with the weapons I had at the end of Outskirts. Will I receive the completion credit soon?
Update: The game lists me having completed the level on Legendary. I guess I did not realize it before. However, the achievement has not unlocked. I did a speed run on Easy with the Scarab gun on, but no achievement still.