The unhinged way Battinson fights he could easily kill almost anyone, no? Not intentionally perhaps, but he’s kind of a maniac when he fights.
Broader point:
If Batman was real… and yes, I know, I know, it’s fantasy but if there isn’t some sense of “this could be real” it’s just pure silliness… he’d regularly end up taking lives of people that are trying to kill him just in self-defense.
Imo that’s basically what Snyder ran with in BvS. In BvS Batman had been doing his thing for 20 years and due to Gotham’s corruption (“criminals are like weeds,” bat-branding of the most heinous offenders serving as a death sentence in prison) and Joker killing Robin (Bruce evidently carries guilt about it as we see when he glowers at the Batsuit in BvS and from his conversation with Joker in ZSJL) he’d come to feel numb about it. He evidently wasn’t particularly troubled if someone that’s trying to kill him gets killed as he defends himself. That sense of emptiness and loss of purpose in BvS is rather like the existential crisis of midlife retired Batman in Frank Miller’s TDKR.
But nevertheless this is indeed a “fall” from his original noble ideals about what it means to be Batman, and to fight crime that way. He’s “fallen.” That sets up a redemption arc. And no, for what Snyder was doing with an elseworld five film saga, personally I did not need to see it developed with solo films. If others want that, nothing I can do about it. But I didn‘t need to see that done first.