What Pokemon have multiple forms in battle?

What Pokemon have multiple forms that can be used and changed in battle. I would appreciate if you include megas as I do not know all of them. Some examples include battle bond/Ash Greninja or zen form Darmanitan.

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–Via Mega Evolution- Venusaur-Charizard-Blastoise-Alakazam-Gengar-Kangaskhan- Pinsir- Gyarados-Aerodactyl- Mewtwo-Ampharos-Scizor-Heracross-Houndoom-Tyranitar-Blaziken-Gardevoir-Mawile-Aggron- Medicham- Manetric- Banette- Absol-Latias-Latios- Garchomp- Lucario- Abomasnow- Beedrill-Pidgeot- Slowbro- Steelix- Sceptile- Swampert- Sableye- Sharpedo- Camerupt- Altaria- Glalie- Salamence-Metagross- Rayquaza- Gallade-Lopunny- Audino- DianceVia other Held items-Kyogre (Blue Orb)- Groudon (Red Orb)- Dusk and Dawn Nezcroma (Uses Ultranecrozium Z)Via Weather- Cherrim (Harsh Sunlight)- Castform(Any Weather)Via some condition in Battle- Darmanitan (Zen Mode Ability, below half HP)- Meloetta (Uses Relic Song in battle. Only changes to Aria Form. Can’t change back until Battle ends or faints.)- Greninja (Battle Bond Abikity, causes an opponent to faint)- Aeigislash (Uses Attacking moves for Blade form. King’s Shield for Shield form)- Zygarde (Power Construct Ability, below half HP)- Wishiwashi- (Reverts to solo form at the end of a turn if below 25% HP)- Minior ( Core to Meteor Form when sent out to battle or at the end of the turn and above 50% HP. Changes to Core form of below 50% HP)- Mimikyu (Disguise to Busted Form if hit with an attack)- Cramorant (Gulping Form- Uses Surf or Dive with at least 50% HP. Gorging Form- Uses Surf or Dive with less than 50% HP. Reverts to normal once hit with a move)- Eiscue (Ice Face-> Noice Face. Hit with a Physical Move. Ice Face is restored in Hail)- Morpeko- (Switches between Full Belly and Hangry Mode at the end of every turn)Others- Dynamaxing. 3 Turns once you click the Dynamax option. Makes you grow large and increases HP stat. Lets you use Max Moves. Only available in certain areas like Max Raids.- Gigantimaxing- Like Dynamaxing, but these Pokémon have access to an exclusive move. These are the Pokémon.VenusaurCharizardBlastoiseButterfreePikachuMeowthMachampGengarKinglerLaprasEeveeSnorlaxGarbodorMelmetalRillaboomCinderaceInteleonCorviknightOrbeetleDrednawCoalossalFlappleAppletunSandacondaToxricityCentiskorchHattereneGrimmsnarlAlcremieCooperajahDuraladonUrshifu both forms.

Note that Eternatus can Eternamax, but this unavailable except for that 1 battle. I may have missed 1 or 2, if I did, please comment.Source:https://m.bulbapedia.bulbagarden.net/wiki/List_of_Pokémon_with_form_differences