Ghost types are weak against other ghost types and dark types so use those types to defeat that elite four member.
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.
After you defeat the Elite Four.
get some good pokemon with good move
Defeat the elite four, Get all 386 pokemon.
Red is the boy playable character in leafgreen you don't defeat him because you are him.
To play in trainer hill you have to defeat the elite four and then when you go there it will be unlocked.
Defeat the elite four and become Pokemon champion with 60 Pokemon recorded in your pokedex.
You have to get the rainbow pass which you cannot get until you defeat the elite four.
If you chose Squirtle as your starter Pokemon. Defeat the Elite Four and it'll roam freely in Kanto.
get all the super effective types including for last one and defeat everyone and save
You must defeat the elite four and the Pokemon champion then catch all the Pokemon which is only possible with help from friends.
They're on the FIFTH island.