She has a terrible costume design. It was good that they tried to get away from the overly likewise outfit designs that most modern-day superheroines seem to have, but they tried a little too hard to make her look sexy.
Her backstory in Suicide Squad is disturbing for a PG-13 movie. It's almost like the film was filmed to be rated R but was cut down to be PG-13 to make more money.
She was hit very hard by flanderization. For example, during Birds of Prey, her passive personality was turned up to eleven to the point where the film has to push her through random events.
Her "crazy" persona is cartoonishly over-the-top and inconsistent.
Her constant monologue in Birds of Prey, which prevents the other characters from being relatable, only serves as a shamelessly added Deadpool reference that ultimately came out as flat.
Like many of the other Suicide Squad members, she's barely characterized as being affably evil, or even anti-heroic.
Much like Rick Flag, Amanda Waller, and Katana, she is not imprisoned with the rest of the Suicide Squad, making the whole movie utterly pointless since nothing changed from the beginning.
Her characterization in Birds of Prey looks like nothing but a copy-paste of Jack Sparrow, without whatever that makes him well-written inside.
Margot Robbie does an amazing job portraying her.
Her comic book counterpart is somewhat better or more decent.
She is more likeable (well, somewhat in the first part of this entry) in Birds of Prey and has improved significantly in The Suicide Squad.