Ivy, especially after the stuff she's been doing in Gotham City Sirens.
She can turn a single leaf into a monstrous plant that she can manipulate with her mind. These days she's a protector of the Green, though not nearly on the scale of Swamp Thing.
MMM I dunno. I didn't really care for her until I started reading Sirens. She didn't stand out much in Harley's old ongoing, but she's getting some nice development in the "mostly plant, little bit human" department.
Her only real weakness is lack of sunlight at present. Cutting her open won't do many brawlers much good; she bleeds poison and acid lol.
She's mostly made out of plant matter now and can manipulate it at will. In a realistic scenario he wouldn't get close to her though, and cutting down the plants to get in will just piss her off. I don't know if even his healing factor can handle the kind of stuff she can synthesize on a moments notice.