Here is the full list of all 14 Concurrency achievements.
Reach the loading dock
Blast your way through the swamp
Piece together the puzzles
Escape the purple haze
I mean, who'd even notice you're gone?
Finish a single hall
Finish ten halls in one sitting
Finish fifty halls in one sitting
Get the most expensive upgrades for the gun and sword
Get an electric chain kill
Grab your gun and bring the cat in
He can't have gotten far, right?
Take the scenic route
Beat the game