Any good examples when the fanbase suddenly changed opinion about a Pokemon or was proved to be wrong about it?

One of the best examples would be Serperior imo. For a long time seen as shit untill its HA version was released and suddenly its one of fan-favourites.

Another thing would be Zygarde which lots of people thought its done because it didnt get Z and its forms were seen as anime exclusive untill few days ago

Other examples?