This is Porygon β's Base FormeBio:
After Porygon's initial release, Silph Co. began development for a successor to Porygon, a number of different Porygon strands were created, the most famous of these was Porygon2. However an almost unknown progression of the Porygon resulted in Porygon β, designed as a guard to counteract and destroy viruses and computer errors, it was never released and was thought to have destroyed during the Rocket takeover of Saffron City. However a small group of passionate scientists managed to smuggle the data containing a number of different Porygon forms out of Kanto, into the Farrof region, where Rocket presence was minimal. Here they worked in secret on finalising Porygon β.Neutralize
: Upon entering battle, Porygon β assess the opponent's stats, it will then change into a specially designed forme in order to counteract the opponent's highest stat.
Attack Forme - Defence Forme
Sp. Attack Forme - Sp. Defence Forme
Accuracy Forme - Speed Forme
Evolves from: Porygon Trade w/item Prototype Dive
Porygon β (C) Concore
Porygon/Porygon2/Porygon-Z/Pokémon (C) Nintendo/GameFreak/The Pokémon Company.