Crossovers between superheroes from separate publishers might not be as common as they used to be, but they're still the source of some of comics most memorable meetings. While Spawn and Batman haven't encountered each other too much, there's been a bloodbath ever time they've met.
The two first met in 1994's Spawn/Batman by Frank Miller, Todd McFarlane, Steve Oliff, Olyoptics, and Tom Orz, itself was written as an extension of Frank Miller's Dark Knight universe. The story begins with Batman in the midst of one of his patrol missions, having just taken down a gang of criminals hoarding high tech weapons in a warehouse. Batman takes in just how much firepower is around him, stopping to examine a pair of battle gloves before being attacked by a deadly cyborg assailant.
It inflicts serious damage on the Caped Crusader before Batman destroys the cyborg and looks to find out who the poor soul fused with the machine is. Batman's investigation brings him to New York, where he witnesses Spawn defending a vagrant in a gruesome fashion, and assumes that he's a villain. The two fight fiercely, but Batman isn't able to hold his ground. Spawn goes on to investigate on his own, uncovering the mastermind is Doctor Margaret Love, founder and president of the Heal the World foundation. The two heroes come to blows once more, but this time Batman is prepared. This moment is exactly the one that Doctor Love needed to send in one of her cyborg assassins, the same ones she's been secretly harvesting the homeless from her shelters to power. Al destroys the machine, but Batman is dying, and so he uses his powers to heal and connect with him, sharing their histories and making it clear that they are on the same side. Finally working together, they're able to put an end to Doctor Love's plans, saving the city and even possibly the world.
Just a month after the release of Spawn/Batman, the two heroes again met for the first time in Batman/Spawn: War Devil by Doug Moench, Chuck Dixon, Alan Grant, Klaus Janson, Steve Buccellato, and Todd Klein. This time, Spawn is drawn to Gotham City by memories of a man he killed years ago, all while Batman is going undercover as Matches Malone. Batman has already stopped a shipment of explosives that were coming into the city, and now a series of shady real estate deals have him particularly on edge, wondering what the connection is. The two heroes cross paths while both staking out Gotham Tower, coming to blows almost immediately before Spawn's living armor decides to make it a fair fight by cutting off Al's powers. After trading blows, they come to understand they're both undertaking the same mission, and work together to get to the bottom of things.
They discover that Simon Vesper, the man Al had killed six years ago, has been resurrected. He's also been buying up prime real estate in Gotham, getting ready for something big to happen. As Vesper speaks to a room of the city's wealthiest, the city streets take a turn for the worst. The dead have risen from Gotham's cemeteries to the delight of Vesper. The crowd around him is shocked by his dark and maniacal shift, and Vesper becomes violent, gouging a man's eyes out before Batman and Spawn arrive. Vesper reveals himself to be the demon Croatoan, having hired Al all those years ago to help his plot along, acting to add new souls to the ranks of Hell's army and bring about his triumphant return. With a timely assist from Batman, Spawn can eradicate Croatoan, sealing the doors to Hell, and sending the walking dead of Gotham back to their final resting places.
It's been over two decades since Batman and Spawn have had a proper meeting, but that doesn't mean their experiences haven't left a lasting impression. Mortal Kombat 11 features a nod to their history together in a match intro exchange between Raiden and the Hellspawn, wherein the former tells Al that he reminds the elder god of another "Dark Knight," to which Al responds that he and the "billion-dollar crusader" are good friends.