Avatar of the Green. Complete awareness of and control over all plant life. Plus several other supernatural powers added on top of that. There's no way any one of the others could protect you in a forest from him. A vine sprouting from the ground could suddenly impale you. Poisonous pollen could suddenly fill the air and kill you. Some mold might suddenly grow all over you and devour you. The salad you had for breakfast might start to grow rapidly in your stomach and tear you apart. Etc.
And Swamp Thing would be able do all these things without even having to manifest himself physically. No way for your team to even fight back.
Gender: Female Location: Poppin Pills on the Rainbow Bridge
You know DS I also choose Walter because of Tanaraq, I had forgotten about his intelligence. I almost chose Man Thing over ST because of his bfr abilities though.