Displacement is a function of deadweight. The higher the deadweight, the higher is the displacemnt. However it does not offer a good insight in the size of the ship in terms of dimensions. A standard VLCC carries 320000 DWT these days so loaded displacement would be about 360000 tonnes. Typical dimensions are 330 meters overall, 60 metres wide and 30.50 depth.
A Triple E Maersk ship has a DWI of about 195000, same beam,same depth but roughtly 70 meters longer. Lightship would be probably around 40-45000, but I have no data on that.
So really displacement is not going to give you a proper size indication. And for more extrme figures, just look at cruise ships, which have hardly any deadweight to speak of.