Smell Fear

You cannot cast Smell Fear without any targets just to proliferate. You must choose at least one creature you control as a target to cast this spell. If you don't choose a creature you don't control as a target, no fight will occur.

If you choose two creatures as targets with this spell and only one target is legal as the spell resolves, no fight will occur and no damage will be dealt, but you will still proliferate.

You don't have to choose every permanent or player that has a counter, only the ones you want to add another counter to. Since “any number” includes zero, you don't have to choose any permanents at all, and you don't have to choose any players at all.