Don't get me wrong, this is not against Jared Leto, I actually enjoy his acting and think he is very talented. No, the joke here is the new design for the Joker. It's not even the fact that they changed his looks for the movie, because yes, in order to refresh a character for a new adaptation, sometimes new character designs are warranted. The failure here is in the design being completely out of character for the Joker. Why create a design that seems more like the result of an angsty teen begging for attention than a truly psychotic menace bent on causing chaos?
For starters, the Joker just would not believably be the sort to have the words "ha ha ha" written on himself repeatedly....if anything, maybe (and it's a big maybe) HE might have tattooed it himself, but for that scenario to be believable, the tattoos would need to look self inflicted, messy, upside down, or just at an angle he himself would have written at. All the tattoos they've shown look too nice, and considering the hours each piece would have taken, in what universe does it make sense that the Joker would sit patiently to have so many tattoos done? The Joker just would not have had this done...he'd be far too busy with all his scheming to bother with taking the time out to get a tattoo, let alone the tons they've shown on Leto's portrayal.
With the matter of his tattoos being so far fetched, what makes it so much worse is that they also sullied his iconic menacing smile. For a villain that is well known for his devious grin, plastering what looks like a grill onto him is just insulting. Overall, it just doesn't make any sense. The Joker is one that seemingly makes no sense in the first place, but there is a method to his mayhem and a pattern to his persona. The character design portrayed follows neither and instead makes the Joker look ridiculous and laughable.