You have to beat the original champion in the game
Gary until you beat him and then you get put into the hall of fame and you become champion
technically, when you beat the Pokemon league, you become the champion. but you cannot really fight as a part of the Pokemon league
the sinnoh league champion. defeat her and become the champion.
Go to the Pokemon league and become the champion
In order to become the master of the Pokemon League, you must defeat the Elite Four and the current Champion. You will then become the League Master. However, when you go back to the Pokemon League, you will fight the Elite Four and the previous Champion as though you never became the Master of the Pokemon League.
In the Pokemon league.
You get your very own Pokemon and you travel around the region trying to become the Pokemon League Champion and complete your Pokedex.
Your rival is the champion.
beat the Pokemon league
You must defeat the Elite Four and the League Champion.
The strongest trainer in the game besides the one's in trainer tower is your rival is the current champion of the Pokemon league if you defeat the elite four you have the opportunity to defeat him.
ummm you can't. you can pretend to have one if you beat the Pokemon league and you become the champion