you go to prof.oak`s lab then talk to him then he will show you the three kanto starters bulbasaur charmanda or squirtle bulbasuar is the best
He disappears until you beat the Pokemon league again.
Earn the national Pokédex, go to the mountain where Red is and beat him.
after you beat red in Mt.silver
beat elite four rematch
he is strong so train your Pokemon alot.
pokemon soulsilver-you get it when you beat red then go to prof.oak in pallet town.
beat red and go to prof. oak
You can always catch Groudon. And Rayquaza too.
first you beat all 16 gyms go beat elite four beat red and he will be at the embedded tower after you get the red orb from mr. Pokemon
I think it's beat red
If you beat trainer red go to Mr Pokemon's house and he will give you a red orb.
If you mean how to consider yourself as beaten the kanto region in pokemon soulsilver, then you should find zapdos,moltres, and articuno. You should also beat Red (Ash Ketchum). Once you do that, you can catch Mewtwo.