Left 4 Dead: Expert

I have researched several ways to get through the campaigns on expert.  Three out of four of the campaigns can be exploited to get through.  Blood Harvest can possibly be exploited but it has it problems.  With Blood Harvest it is about using a good strategy that will let you deal with the hordes of zombies and the two Tanks.

No Mercy: You can use the “Jesus Room”

This is by far is easiest way to get through and you could possibly get the “Untouchables” achievement if you are careful.  The only way this room becomes available is by the zombies breaking down the door.  Getting to this point is a little tough if you are playing on expert.  In my personal experience the subway is the hardest out of this campaign.  You can pretty much count on fighting a tank.  On just about all the times I have played through the tank (the spawn is random) has come at me on the home stretch.