I'm going to have to actually explain this one, because just saying someone would win is a bit boring.

Captain America is a peak-human supersoldier containing a shield forced from the tears of fangirls and Wolverine's solidified musk. Captain Planet is a godlike gestalt entity forged from the combined hopes and dreams of five teenagers and the divine might of the God of Nature herself, and though he refrains from lethal force and is weakened by coming into contact with hazardous substances (and AIDS, I guess), there's no illustrated upper limit to his power.

With his compunctions against lethal force gone, Captain Planet turns Captain America into America's best tree.

The Power Rangers versus the entire population of Canada.