Is it just me or is there something off about this art? Batman is using his left fist but the Joker is knocked backwards as if he had been hit by Batman's right fist.
In context of the whole story arc, I think this is a perfect panel. Right down to Batman using the "wrong" fist, and using excessive force. This story is "the breaking of the Bat", after all.
It's intentional. Batman is off-balance and a half beat behind for this whole story arc.
Hitting Joker with his off fist, and revealing his true rage, is evidence that his methodical calculated master strategist is chipping thin, revealing the raw broken child underneath, who is simply desperate to prevent what happened before from happening again, at any cost.
spoiler for Kightfall
It's why Bane is able to casually walk into his home and break him in half in the next (chronological) issue.
This is an interesting and good characterization, but I don't think the point of the comment. Just in terms of physics, punching with the left fist, for whatever reason, should have flung Joker to his left, not right.
