There are several notable power-ups available in the Pokémon franchise, and arguably the coolest of all these is also the most horrifying. Pokémon’s power-ups are all visually striking in their own ways, making each unmistakable and unique. However, it is worth noting that none of these additions have remained a truly permanent part of the franchise by appearing in all subsequent games; as a result, each of these power-ups is best described as simply being a gimmick in the long run.

https://screenrant.com/pokemon-mega-evolution-dark-pokedex-entries-op-ed/