I would say Groudon or Kyorge or deoxys or Jirachi or mew or mewtwo or rayquaza
YES, YOU DUMMY!(after you defeat the Pokemon League and get the Ruby/Sapphire.)
defeat the pokemon league
yes swarpert is a greatest Pokemon to defeat elite four
As soon as you defeat the Pokemon league, you can find Latios roaming around in the wild. You can also get Latias in Pokemon Sapphire.
swampert or blaziken are the best type to beat gyms or Pokemon league
Get the Goundon
have a strong fire Pokemon or fire move
On Ever Grande City
The Pokemon League
by fighting
you can only defeat them after you have won the Pokemon league they break nto a cave and through there is a ruby . Adz
you only have to beat the elite 4 on Pokemon fire red not ruby