239 ELEKID
During the development of G/S, Game Freak ran out of ideas for new Pokemon and could go two ways - invent awesome evolutions of existing Pokemon or shitty pre-evolutions of existing Pokemon. They chose the latter. It took them another 2 generations to rectify that error, thus inexplicably leaving Pokemon like Elekid in the middle of the national dex while its evolution is at the beginning of it and the evolution of that at the other end.