Harley's immunity to toxins and enhanced strength and agility, which were gained from a special formula created by Poison Ivy, were carried over from Batman: The Animated Series, with Dini stating that they would give her a sort of "physical edge" over Batman and other heroes.
Metahuman Physiology: Harley Quinn was injected with a special toxin antidote by Poison Ivy, which resulted in her becoming immune to various forms of chemicals, such as Ivy's pheromones and Joker Venom. The injection also gave Harley enhanced her physicality, making her a formidable hand-to-hand combatant.
Harley Quinn is a total badass. She's a skilled fighter and has an arsenal of weapons at her disposal. She's not afraid to take on anyone who gets in her way, and she does it all with a sense of style and humor that is uniquely her own. Finally, one of the best things about Harley Quinn is that she's empowering.
This is how lore accurate Batman would've beaten the Suicide Squad (Animation)
What is the weakness of Harley Quinn?
Weakness: Harley Quinn appears to be fearless, yet she doesn't have enhanced strength, speed, or metahuman powers, making her vulnerable to physical attacks from her more powerful opponents.
Harley and the Joker are eventually defeated by Batman and Catwoman, and Harley is last seen being wheeled away while bound in a straitjacket and muzzle.
While they were dating, one of the most frustrating things for Harley was Joker's obsession with Batman and his lifelong goal of playing and eventually killing him. Back in the original, classic stories Joker and Harley Quinn they have together, Joker abused her the most when he didn't want Batman touched.
Despite appearances, Harley Quinn has been able to go up against (and defeat) powerful opponents like Lobo, Black Canary, and even Superman. One of her most defining traits is her unpredictability, something she often utilizes to her advantage against stronger opponents.
The Joker is one of the most dangerous and most evil villains in comic book history, having caused untold amounts of destruction on Gotham City and the world at large, but even the Joker admits that Harley Quinn is a better super villain than he could ever be.
She is now her own person and despite her insanity, is heroic and noble as she helps people who need her help. She also protects innocent people as well, and is living her own life working as psychiatrist who helps people when not on the job as a superhero.
She effectively killed Superman before he ever got a chance to become the hero he was meant to be. While it's not as impressive as defeating the Last Son of Krypton in his prime, killing Superman is something that technically puts Harley in the same league as Doomsday.
Although she mainly relies on her physical abilities and infamously reacts with her emotions rather than thinking things through, Harley has proven to be a very intelligent character. As a doctor and a trained psychiatrist, Harley uses her psychology skills to help get herself out of trouble.
While the two worked together for years, the only one keeping any semblance of a relationship alive was Harley. Truthfully, the Joker was never that interested in Harley, save as someone he could easily leave holding the bag during his criminal endeavors.
During more sessions, Harley's mind started to snap as her infatuation for the Joker grew, until one point, she helped him escape, dressing up like a harlequin jester to further try to endear herself to the psychopath, knocking out several guards in the process and taking on the new persona of Harley Quinn, the Joker's ...
when she was involved with “The Joker”…it was the Batman himself! Now, however, since Harley has essentially emancipated herself from the Joker's manipulative, violent, abusive, and pernicious behavior, “The Joker” has himself become her arch-nemesis, and, The Batman, who was once her enemy…has become her ally!
Harley Quinn finds fulfillment helping villains find healthier ways to be bad. Her new role reveals a passion for educating and guiding others, a positive turn in her journey. Harley's shift from hero to antihero allows her to make a difference in a unique and impactful way.
Whether that means throwing herself at the cat or simply blowing up a building to try to crush her opponent, Harley Quinn will destroy everything in her path to win a battle. As seen in Suicide Squad, she has extremely destructive tendencies and would use those to her ability against Catwoman.
The story "High School Lows" from DC Saved by the Belle Reve #1 (by Tim Seeley, Scott Kolins, John Kalisz, and Wes Abbott) reveals that Harley's worst fear is a truly corrupted Poison Ivy (aka Pamela Isley).
Aside from the fact that he is a monster with no cause other than gleefully causing destruction, she has a much more personal reason to despise him -- his abusive behavior toward Harley Quinn.
Her love for the Joker inspired Harleen to adopt a new identity, that of Harley Quinn, the Joker's sidekick-slash-love interest—whether he wanted one or not. (Most of the time? He did not.) In time, Harley came to realize the Joker was holding her back and she struck out on her own.
