Did they? Keaton didn't seem to give a rat's about bringing his bad guys in alive, henchman or rogues. Kilmer (from what I recall) doesn't kill henchman but does "trick" Two-Face into falling to his death. Clooney...hell if I remember, but I don't recall him killing anyone. Bale didn't tend to directly kill anyone, but he didn't seem to care much one way or the other.
Affleck and Keaton are the only ones where I recall them really digging in and killing with reckless abandon. As much stick as I give Affleck's Bat and his regard for life, he'll never equal Keaton setting off bombs between the legs of goons, burning clowns alive, and attaching dynamite to fat guys.