An object's weight would be the greatest on the Sun. Weight is determined by the gravitational pull that a body exerts on an object, which varies depending on the mass of the celestial body and its size. The Sun has a much greater mass than Earth, Pluto, or the Moon, resulting in a stronger gravitational force and thus greater weight for an object located on its surface.
In comparison, the gravitational pull on the Moon is much weaker than on Earth, and both Earth and Pluto have less gravitational pull than the Sun.