It's hard to be sure who stole from whom, but Marvel's Man-Thing came out the same year as his DC rival, Swamp Thing. Both were born from some industrial accident involving death and being regenerated by swamp organisms fed by experimental chemicals. Both dealt with the understandable difficulties of interacting with ordinary humans. Basically, apart from being more interesting to draw, these guys were not far removed from The Thing or The Hulk. So maybe I gotta weigh in on Marvel's side here, though in the long run Swamp Thing turned out to be way more interesting. Man-Thing's unique abilities included oozing, secreting, and creating a corrosive excretion whenever he sensed fear in humans. I'm sorry, the corrosive stuff is so-so, albeit with the drawback that he can't do it at will, but all the other stuff is not cool. Oozing and secreting are not super powers!