Early on in Suicide Squad, Amanda Waller makes an offhand comment about Harley Quinn being “crazier” than The Joker, and “more fearless.”
Make no mistakes, Harley Quinn is certainly unhinged (we can thank The Joker for that), but between the two of them, she is the one who keeps a hand firmly gripped on the monkey bars of sanity.
While that’s certainly a badass sentiment to describe a character who will go on to become one of the film’s greatest anti-heroes, the fact of the matter is that it’s simply not true in any depiction of the Joker and Harley dynamic.