Including forms like Dusk Mane Necrozma.
[Gen 1-6 is covered in this existing question.](https://pokemondb.net/pokebase/218503/what-are-all-pokemon-that-decrease-stats-while-evolving
This has a list of everything up to Diancie, so I'll only put Alolan Pokémon.
That's everything from Alola.