“David [Ayer] really wanted her to be strong, badass and nuts – but fun as well. Whenever I would be inclined to play into the comedy or play her more likable, he’d always direct me the other way. He wanted her to be pretty vicious.” - Margot Robbie
I think this quote clearly illustrates what’s wrong with Harley’s characterization in BOP. Without David Ayer’s direction, Margot does not have the instinct to play Harley as a fleshed out villain, instead she plays into the likability factor to a fault.
David Ayer really understood this layer of malice under Harley’s bubbly persona and wrote her as a very complexe and engaging character. What I liked most about Harley Quinn in SS is that she had her funny moments, sure, but she also had this really somber moments where we could clearly see she was a smart and strong woman who knew what she was doing.