only one??
well, there's the clown you mentioned -- that guy, he flat out murdered.
but there were several other non-batman lethal (or lethal-like) attacks, tho. (granted, "no body, no death," but...) such as the "batmobile fire exhaust blast to the face" in batman returns, or dropping the thug down the bell tower in batman. how about using the batmobile bombs to blow up a factory filled with baddies?
plus, there's the fact that just about every supervillain dies in the movies.
one of batman's major aspects is NO dying. no killing. doesnt matter if you tried to kill him for 90 minutes, he'd still save you. the comic book batman would have swung via rope to save the joker (etc).
this is more or less the reason for this post... the batman (namely just the 89 movie version) was pretty different from all comic book adaptations.
he was much more grim, wore an all black suit, didnt really work with police (all be it in a "i dont know you yet" fashion).
he was also much more violent at times (the above maimings / killings -- slapping machine guns on the batmobile, full out shooting at the joker in the batwing, with missles no less!)
buuuut... is that a bad thing? i mean, they made no claims that it was the comic book version of batman. it was a great, stand-alone movie, that told a story and got people interested in the character.
there was obviously a lot of effort put into the casting, acting, scenes, musical score, etc. and, there wasnt the emphesis on tie-in sales back then, like there are now.
good far outweighs the bad, in this case.