The Atrium

The Atrium Finale has the Survivors collecting gas cans to fill a Racing stock car in order to escape the mall in a similar manner to Scavenge Mode. After starting an elevator to get down to the car the survivors are immediately mobbed by hordes of infected while trying to get gas cans. The amount of gas cans remains at 8 regardless of difficulty. The number of gas cans needed may change, dependent on the number of Human players in the group during Online campaigns. In single player mode, the non-player survivors will not attempt to fill the car up with gas due to the fact that they're protecting you from incoming hordes.



Strategies
One way to make things easier is to toss the cans over the rails next to the car. That way, you can fetch the more remote cans faster and also do the refueling all in the one run. Although this is risky, shooting a gas can may start a fire which spreads if the cans are too close. However, the gas cans respawn again in their original place.

In addition, work in pairs instead of as a group when throwing the cans down to spread out the horde and make the process quicker; the horde is focused on the center of mass of the survivors, and pairing up will spawn the horde farther away and in fewer numbers.

When a Tank comes in throw molotovs in the direction a block of concrete flys at you.

For Versus here are a few things to consider

Boomer: Anyone playing as a Boomer should stay hidden until the group is either together fully or one person is alone. When the time is right use the vomit attack on the team/loner and claw at 'em until death Hunter: Wait until someone seperates themselves from the group completely and pounce them when they either find a gas can or are out of sight to the rest of the Survivours. If a smoke has somebody already pounce someone else Smoker: go to the highest point possible then use a tounge attack on the first Survivour you see. Alert anyone who is a Hunter to pounce someone else and wait patiently. Jockey: Quickly jump onto someone then lead them far away (preferably into Spitter Acid) Charger: If he entire enemy team is jummbled p and close together use the charge attack to not only send everyone flying but cause massive damage to a specific person Spitter: Like the Charger's stratagey, wait for everyone to cluster together into 2 or more people and use the spit attack and claw at everyone randomly Tank: When you are picked to be the Tank, charge at the survivours and use a heads to call in for backup against healthy players. Take out anyone with a gas can first then aim for the rest.

Trivia

 * This is currently the only campaign ending in Left 4 Dead 2 to have "finale" in the title, like the ones from the original Left 4 Dead.
 * The stock car and its driver are likely references Dale Earnhardt Jr., a NASCAR Sprint Cup driver who drives the 88 car and Richard Petty who drove a Dodge Daytona and a Plymouth Superbird in 1969-70, respectively, in NASCAR with the characteristically huge spoiler and blue paint.
 * An Uncommon Infected is Jimmy Gibbs Jr. himself. He is said to have 1000 health and will spawn, though only once and very rarely, he is immune to fire and covers your screen with motor oil like a Mudman. The Survivors also have special lines when seeing his zombie.
 * Oddly enough, when stepping out of the elevator, you are told "Rescue is Coming, Defend yourselves!" even though you're required to fill up your vehicle.
 * Left 4 Dead did this as well, when you refuel the plane in Dead Air during the finale, it says "Rescue is Coming, Defend yourselves!" even though it's sitting right in front of the fuel tanker.
 * The Hazmat infected do not spawn in this chapter.
 * Do not put gas in the car while being healed, this causes the game to freeze.
 * Interestingly, while in the glass elevator, Ellis will explain his plan to escape the mall which is to use Jimmy Gibbs stock car. Part of the plan is to "find the car" even though it is clearly visible from the elevator (as is the layout of the atrium).