Games like Alien Swarm

"Killing Floor" is a cooperative survival horror game set in wave-based scenarios. Players fight off hordes of enemies, known as Zeds, using a variety of weapons. The game features a class system, where players can specialize in different roles to better survive the onslaught. As players progress, they can earn money to buy better weapons and equipment for the next wave. The ultimate goal is to survive all waves and defeat the boss Zed.

"Left 4 Dead" is a cooperative first-person shooter where players fight hordes of zombies in a post-apocalyptic world. Players work together to survive and reach evacuation points while battling against different types of infected enemies. The game features a dynamic AI director that adjusts the difficulty and pacing of each level, creating a unique and challenging experience.

"PAYDAY™ The Heist" is a first-person shooter where players step into the shoes of a career criminal, pulling off intense heists alongside three other Co-Op partners. The game features six high-stake heists, each with its own challenges and objectives, and offers a massive character progression tree for building skills. With endless replayability, hostage trading, and additional DLC content, "PAYDAY™ The Heist" provides a thrilling, action-packed experience.

"The Red Solstice" is a tactical, survival-focused game set in a sci-fi universe. Players explore an alien planet as a member of a marine squad, fighting off hordes of hostile creatures. The game features real-time with pause gameplay, allowing for strategic decisions during intense combat situations. Co-op multiplayer is supported for up to 8 players, promoting teamwork and communication.

"Aliens: Fireteam is a third-person survival shooter set in the Aliens universe, where players battle through four campaigns with up to two additional players or AI. The 'Into the Hive Edition' includes a new campaign and the 'Ultimate Edition' offers additional DLCs, weapons, and the full suite of Endeavor Pass cosmetic DLCs. Build your fireteam and explore the mysterious planet LV-895."

"Earthfall is a Science Fiction Shooter game with single-player and multiplayer co-op modes for up to 4 players. Battle an extraterrestrial invasion in the Pacific Northwest using futuristic weaponry and deployable barricades. Experience tense, procedurally generated gameplay and a well-crafted story across 15 levels."

"World War Z: Aftermath" is a co-op third-person shooter game based on the film, where players battle swarms of hundreds of zombies in fast-paced gameplay across various locations worldwide. The game features a new first-person mode and gore systems for satisfying action. Humanity is on the brink of extinction, and players must band together to defeat the horde and outlive the dead.

"The Pit: Infinity" is a rogue-like, sci-fi shooter that pits players against hordes of alien creatures in a procedurally generated arena. With a wide range of weapons and abilities to unlock, each run offers a unique and challenging experience. The game also features a permadeath system, adding an extra layer of tension and strategy to the intense combat.

"Contagion" is a horror survival game with dynamic gameplay, where each playthrough is unique due to its built-in randomization system. The game features state-of-the-art gore and immersive sound effects, bringing the dark atmosphere of a zombie apocalypse to life. Traditional zombies and various game modes provide an intense and addictive experience.

"Killing Floor 2" is a shooter game with great mechanics, impressive graphics, and a memorable soundtrack. It offers both single-player and multiplayer experiences, including co-op and PvP modes. With frequent updates bringing new content, such as the Polar Distress, Blood & Bonfires, Tidal Terror, Chop 'Til You Drop Xmas, Day of the Zed, and Interstellar Insanity updates, the game is highly replayable and builds a dense, emotional atmosphere, despite some bugs and grinding.