The HBO Max animated series Harley Quinn features an incredibly powerful Poison Ivy, taking elements from several different versions in the comics. Ivy easily counts among the most powerful supervillains in the DC Universe (depending on how she's perceived), but some Ivy versions possess more power than others.
Ivy generally uses her power to control plants against Batman in relatively low-stakes schemes in the comics, but modern versions connect to The Green, a powerful natural energy source that transforms her into an almost elemental figure. Other versions rely on her cunning and insight, qualities the comics didn't always value, but have proved invaluable in her relationship to Harley.
DC Bombshells
Most Ivy versions in the comics possess superhuman powers, but that's not the case with the DC Bombshells version. Though she enjoys a natural immunity against most poisons and toxins, she doesn't have any powers most versions in other media do. Her green skin comes from exposure to a perfume she concocted to drug Nazi soldiers.
This Ivy does maintain other versions' unparalleled skill in botany. She often uses her skill in tending plants and knowledge of herbs and poisons in the war effort in this alternate reality.
Lil' Gotham
Ivy also seems to lack her typical superhuman powers in the 'Lil Gotham universe where all DC characters appear as child-like versions. She nevertheless possesses the same criminal ambition and capacity, always scheming to pull off a major score or operation, usually with Harley Quinn in tow.
Ivy's logistical and practical sense often goes underappreciated in the comics, but underlines virtually all of her and Harley's successes, especially in the current animated series. Ivy's cool and clear-headedness often keeps Harley on track.
The Original
The original Ivy from pre-Crisis On Infinite Earths continuity gains the power to control men and women with her own pheromones from involuntary genetic experiments. She also contains a toxic poison that can kill on contact that she usually administers through a kiss, though she can deploy it through any physical touch.
Ivy also possesses immunity to any and all toxins thanks to being poisoned with ancient Egyptian herbs. This original origin story, which has been updated many times since, first appeared in World's Finest #252. Ivy's first appearance in comics came in Batman #181, where she initially proved her powers of seduction.
Earth 12
The Earth 12 Ivy represents the iconic version from the best Batman: The Animated Series episodes in comic book adventures. She wields chlrorokinesis, the ability to control all plant life. This provides Ivy with her signature weapon, ready vines that she uses to attack, defend, and most often, apprehend her opponents.
This power evolved considerably in the comics and other media over time. Initially, Ivy's power over plants seemed limited, but as her character evolved, her powers have reached extraordinary levels.
Gotham By Gaslight
The Ivy from the Gotham By Gaslight steampunk reality uses mostly the same powers as the others. Her ability to control plants becomes especially potent in this reality, where practical weapons remain locked in 19th-century standards. She also proves that she numbers among the best martial artists in the DC Universe with her excellent fighting skills.
This Ivy doesn't appear in the original Gotham By Gaslight Elseworlds story, but in a later comic that revisits that world and brings together many other Batman villains from the period.
Harleen
Ivy shares the same basic powers as most comic versions in Harleen, among the best Harley Quinn comic books ever. While most Ivy versions going back to the 1992 animated one feature some insight into Harley's personality, this one reveals how perceptive Ivy truly is. Despite her often overstated misanthropy, Ivy contains deep empathy for others.
Her willingness to see the good in other people usually manifests in Harley and does so in unique fashion in this comic. Ivy's openness allows Harley to help her better understand herself and in turn makes Ivy more empathetic in general.
Gotham A.D.
Mother Panic - Gotham AD introduces an Ivy whose power continued to grow in an alternate future. Her consciousness extended beyond her body into plants and she exists as the entire ecosystem in Robinson Park within Gotham. This park also fell under Ivy's protection in No Man's Land, among the best Batman comic book storylines ever.
Ivy's newfound state grants her power beyond most others in the comics and essentially makes her invulnerable. It does come with drawbacks though as she can only interact with Harley and others through gestures and expressions from plants.
Dark Knights Of Steel
The Ivy that appears in Dark Knights of Steel #5 not only possesses the extraordinary chlorokinetic ability as others, she also ranks among the most powerful magicians in this strange alternate reality. This makes Ivy the absolute ruler in Hobb Forest, the enchanted woods where she resides. Her power likely extends far beyond it as well.
Ivy goes by the title The Lady of the Forest and wields so much power that the House of El effectively leaves her alone. They also don't seem to care that she doesn't protect the forest for their benefit, as it might seem, but only for their court jester, Harley Quinn.
Queen Ivy
Ivy gains perhaps her greatest power in recent comics, when she fully embraces The Green and becomes Queen Ivy. The Green functions as a cosmic natural energy field living in all plant life and grants its users superhuman strength, stamina, and reflexes among many other abilities. Her foremost talent includes the power to manipulate matter and energy, controlling not only plants but people as well.
She accelerates plant growth and death, essentially gaining control by proxy of the seasons. She shares a collective consciousness with plants through The Green and can perceive other places around the world and even beyond from wherever she is. Most importantly, Ivy achieves a kind of immortality through The Green. She can die, but like plants, she grows again and often comes back even more powerful than before.