We have to wonder which demogorgon it is ; the USSR one seemed stronger and faster. But according to the image, I guess it's the Hawkins one. El, Vecna and the Mind Flayer are stronger.
El won a fight against Vecna twice.
So, I think it would be between El and the Mind Flayer, and I bet on this last one because our Jane remains humen whereas the Flayer can give its strenght to all creatures.
Oh, I forgot Mews ! Too late, I voted.
