In the comics and Christopher Nolan's Dark Knight Trilogy, Batman has made it his mission to never take a life. Dubbed his one-rule by his friends and enemies, the term separates him from the criminals he puts away either in jail or Arkham Asylum. That being said, humans are fallible, and even in the films, it's been shown that Batman doesn't always uphold his one rule, but unlike his later appearances, Tim Burton's Batman and Batman Returns totally disregard this rule, turning Batman into a killing machine.
Batman's story in the comics shows him growing from a brutal vigilante to a hero, detective and savior. In Burton's film, Batman is established as a hero, but his acts are largely unexplored by civilians. However, as the viewers, it's shown exactly how Batman exacts justice, and it's unlike anything die-hard fans could expect. Batman takes multiple lives in the first film, but they're mostly circumstantial unless his life is in danger. For example, when he blows up Ace Chemicals by remote driving the Batmobile, there's room for ambiguity in saying he didn't know if it would be occupied, but this isn't always the case, as the film's final battle showcases.
After dispatching the Joker's balloons of Smilex gas, he destroys his parade with missiles and bullets in the Batwing. In one scene, Batman is shown gunning down the Joker's henchmen and blowing up their floats with them still standing on them. Even these moments could be argued, albeit poorly, that he missed, and the bad guys were knocked away by the blast or hit by ricochets because he couldn't even shoot the Joker head-on. However, when facing one enemy at the top of the belfry, Batman tricks him into looking over and pulls him off the ledge to his death.
In Batman Returns, he's even more blatant with his kills. Early on, he's shown lighting a villainous firebreather on fire with the Batmobile's afterburners. Later in the film, he attaches a bomb to another henchman, smiles at him and punches him down a hole where he explodes. Though he's killed fewer enemies in this film, the ways they're killed are far less ambiguous.
As for his villains, he often sends them to their death through circumstance. For example, he gets justice for his parent's death, anchoring the Joker to the rope ladder of his helicopter and a loose gargoyle. Eventually, the gargoyle proves too heavy, sending him crashing to the ground. As for the Penguin, he uses a sound emitter to call bats to him, causing Penguin to panic and fall through a window. Catwoman even claims Batman killed her by throwing her off a building into a sand truck, though that's more up to speculation.
Typically fans will comment on the character's murderous outbursts committed by Batmen like Ben Affleck, but with over thirty years since Michael Keaton's Batman appeared, it's easy to forget that there were far more deadly versions that have been on screen. As videos will show, Keaton's Batman was undoubtedly ruthless, and unlike his future incarnations, this version wasn't afraid to face it.