Torrential rain hits hard just as we double back through the Witch-infested sugar field. With visibility reduced to nothing and the thunder drowning out Coach’s orders, we get separated in the thick crops. I stare in dismay as a rotten waterfall of corpses pours over the side of the mill we’re running towards. I align the barrel of my shotgun head-level with the charging crowd and fire every shell into the obscuring vegetation. Suddenly, a blood-curdling scream fills the air, followed quickly by another. It’s already too late by the time we realize we’ve startled two Witches…

Left 4 Dead 2 is swollen with action that will leave your controller sweaty and worn, and emerges as one of the most powerful online co-op experiences I have ever had. This trek into zombieland boasts more intense combat, finales, crescendos, settings, enemies, and game modes than last year’s title. Four players banding together for survival is still the focus, but the conditions have become far more chaotic.

Left 4 Dead 2 drops four new charismatic zombie-killers in the Deep South, where they endure five uniquely awe-inspiring locales. Players gleefully hack and blast their way through everywhere from abandoned carnival grounds to The Big Easy itself, with each campaign carrying a distinctly different atmosphere of dread. Crescendos, such as a mobile fight along rollercoaster tracks, liven up the standard dig-in-your-heels horde defense of the original. The tense finale of one campaign has the survivors defending a bandstand stage while utilizing a famous rock band’s pyrotechnics to simultaneously ward off the undead and signal a rescue chopper.

Littered across each new setting are brand-new saliva-inducing melee weapons like the katana and frying pan. You have not experienced ghoul-gibbing bliss until you’ve been bum rushed by infected and spun in a circle while wielding a chainsaw. Melee weapons fit so naturally into L4D2 that you’ll wonder how you ever managed the first game without them.

Other useful items and firearms equally expand gameplay. Use a defibrillator on a fallen friend, pump yourself with adrenaline for a life-saving speed boost when you’re in the red, or throw a vial of boomer bile at a charging tank and laugh with twisted delight as nearby zombies tear it to shreds. The standard weapon types of shotgun, automatic, and sniper rifle now feature a broader variety with unique characteristics as well. All these additions combined with the brand new grenade launcher allow your band of survivors to methodically customize your strategy like never before.

Don’t expect the new goodies to allow you to mow through infected like grass; the undead legion has mutated into a stronger beast. The Hunter, Boomer, and Smoker are now joined by three new devastating special infected that add welcome depth to the enemy roster. The Charger plows through the survivors like an irate freight train, the Spitter projectile vomits a pool of noxious acid which does area of effect damage, and the Jockey mounts a human’s shoulders and steers them into nearby hazards. New “uncommon common” infected like the flame-retardant HazMat suit zombies and heavily armored SWAT team zombies put a challenging twist on the generic rabble.

The augmentation of both the infected and survivors makes for some of the most enthralling, white knuckle multiplayer you’ll play this year. Versus stays fresh and balanced with six special infected types to choose from instead of the original game’s three, and even more maniacal laugh-inducing coordinated strikes. The new competitive multiplayer mode, Scavenge, has survivors scrambling to collect gas cans to stop a countdown timer across six maps, with the infected doing everything in their power to stop them. Glorious chaos routinely erupts around the generator as the desperate humans struggle to pour gas into it. As a survivor, you’ll cry out in anger as the tie-breaking gas can explodes after a Spitter pukes on it. As the infected, you’ll cheer as a Charger pummels a gas can out of Coach’s arms during the suspenseful overtime. This fast-paced, round-based multiplayer will have you lurking in game lobbies (which have been greatly improved) until the actual apocalypse hits.

Last November, Valve spread a pandemic infection across Xbox Live and PCs everywhere with the original Left 4 Dead. The newest chapter in the undead uprising now oozes with even more of the proven developer’s trademark personality and polish. If you are among those who think the sequel is coming too soon, prepare to eat your words like so many brains. Left 4 Dead 2 is everything a sequel should be: perfected, expanded, and an absolute riot.