Anyone from the Red Ribbon Army could be dealt with, and probably Raditz too, unless he can also zap planets to nothingness like Vegita can. But after that, Nappa and Vegita (Vegita even at his least powerful as seen then) would wipe the floor with our world’s strongest.
So I say Raditz, and MAYBE Nappa if Vegita isn’t there to coach him. On second thought, Cell too, in his first form, since he needs time to evolve by absorbing people but the military would only stand a chance if they knew ahead of time what they were dealing with.