Acid Downpour is available to Pokemon on a list below.
Garchomp : egg moves / learn by breeding
Steel-type Pokemon
Zekrom DB: stats, moves, locations & evolution
Simisear DB: stats, moves, locations & evolution
Audino DB: stats, moves, locations & evolution
Masquerain DB: stats, moves, locations & evolution
Lopunny DB: stats, moves, locations & evolution