Suggested by Destroyer Swamp Thing is a tough beast of nature but he’s not going to be doing much against Mephiles here. Mephiles the Dark was able to take on Sonic and Shadow while also being strategic enough to have a plan to gain even more power. Swamp Thing won’t be able to hide or endure Mephiles’ attacks for very long and that will result in his being taken down for the count. Mephiles wins.