Looks like those last two campaigns were true to their name as the list of Xbox 360 Achievements
for Left 4 Dead II
show Dead Center and Hard Rain as two that can be had for finishing the campaign. I'd like to know how to honk a clown nose though as there's one for honking 5 clown noses. Do you hit them in the face with a melee weapon?
The new infected also get some achievements as well along with Scavenge specific ones. It also looks like the game now has alarms that should be similar to setting off a car alarm and alerting a bunch of zombies. I think my favorite name for an achievement though has to be Bridge Over Trebled Slaughter,