>first battle
Has friend who always accompanies. Turns out to be Mew pretending to be human when professor needs saving from wild pokemon cliché.
lvl 10 Mew

>second battle
Mew continues to accompany me in human form, opposite gender of protagonist, throughout the game
lvl 12 Froakie(shiny), lvl 20 Mew

>third battle
lvl 19 Frogadier (shiny), lvl 22 Noibat, lvl 31 Mew, lvl 15 Abra

>fourth battle
Saves Charmander from base/facility after assisting protagonist give evil group first major loss. IS absent for a time to take down far off base of evil group while protagonist gets badges and looks for boss.
lvl 32 Frogadier (shiny), lvl 36 Noibat, lvl 39 Mew, lvl 36 Kadabra, lvl 15 Charmander(shiny)

>fifth battle
Assists super old shrine keeper in some religious rights involving comet and shiny Rayquaza rises out of it and chooses me as its trainer. Protagonist is given access to shrine where all trainer battles grant triple exp.Takes monks advice and trains in wilderness because, idk, Rayquaza is special guardian who chose me to make it strong.
lvl 52 Greninja (shiny), lvl 50 Noviern, lvl 55 Mew, lvl 50 Alakazam, lvl 49 Charizard (shiny), lvl 50 Rayquaza (shiny)


>sixth battle(League champion)
Appears as champion after disappearing to wilderness
lvl 69 Greninja (shiny), lvl 66 Noviern, lvl 75 Mew, lvl 66 Alakazam, lvl 70 Charizard (shiny), lvl 75 Rayquaza (shiny)


>post game
lvl 89 Greninja (shiny), lvl 87 Noviern, lvl 95 Mew, lvl 88 Alakazam, lvl 88 Charizard (shiny), lvl 92 Rayquaza (shiny)