Somewhat yes.

when it comes to depiction of cruelty by villains its...complicated

yes hes the villain yes hes evil but cruelty can often be too much for some people and when it comes to reviews which can often be a helpful perspective letting a creator or merely others know that for them the cruelty intended to show off how awful a villain is crossed over into a realm of genuinely uncomfortable and felt less like cruel to the character and cruel to the reader and wanting the reader to feel like the characters suffering from the cruelty which is...a choice that I feel ends up just being trauma porn that does nothing but kinda slightly get off on the idea of how edgy you are.

your argument somwhat also is off kind of. yes hes evil yes hes the villain but those arent defenses those are really honestly just descriptions of the Joker and yes sure he is a lot of those things (one could argue as i do he doesnt need to be because I really hate clown serial killer Joker a lot) but there isnt much of response to that beyond "yes"

cruelty isnt in of itself a problem Abigal Thorne has said once that Rape in media isnt nesscearily impossible to depict it just seems anyone who wants to do it wants people to feel like the rape victim and Ill be quite honest as a victim of sexual assualt nah im good

that isn't to say the Joker one shot did this honestly I wouldn't know because I havent read it but the premise of your thing is slightly flawed tho from what you have described it doesnt seem to have any of those pitfalls so this diversion of a comment is mostly pointless but I wanted to voice my thing anyways.