The The Passing Add-on for Left 4 Dead 2 has 10 achievements worth 250 gamerscore.
Survive The Passing Campaign.
As the Charger, grab a Survivor and crash them through 8 chairs at the wedding.
Using the M60, kill 25 infected without letting go of the trigger.
Collect 10 items dropped by a Fallen Survivor.
Play 6 Mutations.
Knock off the heads of 18 infected with the golf club.
Play the new Midnight Riders song on a jukebox.
Kill a Tank only with damage from the original Survivors.
Open 5 foot lockers.
Play 5 full games of Scavenge on The Port.