I'm going to give you either a random marvel character or a random dc character. All you have to do is give that characters corresponding counterpart. This means the character from the other brand that have the most similarities with the character you are on. I will also give you the similarity that the two characters have. Good Luck!
For Swamp Thing Man-Thing
For Thanos Metron
For Hulk Solomon Grundy
For Lex Luthor Justin Hammer (debatable)
And for Captin America General Glory