Nemesis: Martian Manhunter
Other Major Foes: Superman, Justice League of America
Appearances: 4 comics
Powers: Flight, superhuman physique, and presumably other innate Martian powers.
Bel Juz survived the genocide on her home planet and thrived on Mars II through ruthless cunning, feminine whiles, and a willingness to sacrifice countless lives rather than suffer herself. Superman once saw through her charade and choked her unconscious with considerable effort. Using the Marshal of the Red Brotherhood as a chess piece, Bel Juz orchestrated a Martian invasion of Earth that was put down by an under-staffed JLA.
Win: Dr. Light (8-1); Cay'an (4/1); The Martian Criminal (10-4)
Lose: Scorch & Bette Noir (4-7, 4-8); Human Squirrel (?)
Other Major Foes: Batman Family
Appearances: 600+ comics, toys, video games, animation, and a major motion picture.
Powers: Immunity to poisons/toxins, toxic bodily secretions that can kill/control, plant control, and superhuman physique.
After being betrayed by a man and nearly killed by an injection of plant poisons, Pamela Isley survived and thrived through her intellect and special relationship with plants. Though mad, Poison Ivy has killed and manipulated her way up through the hierarchy of Gotham City's criminal underworld, and run into most every urbabn vigilante under the sun. Ivy tends to target men, and has a weakness for her fairer sex.
Despite the fun I had with the image mash-up topside, Poison Ivy goes down hard and fast. Her forte is plant control, which can certainly ruin a Caped Crusader's weekend, but isn't likely to stall a powerful Martian. Perhaps with time to plan, Ivy could cook up a mind-controlling herb for a Martian the way she did with a Kryptonian, but that took her years to work out. Ivy has nearly as much reason to avoid fire as Bel Juz. Finally, the Martian minx is a green-skinned femme fatale, so if anyone was likely to counter-seduce Poison Ivy, it's Bel Juz.