You can find the Eighth Gym Leader, Clair, at Blackthorn City. But first you will need to battle and defeat Team Rocket in Goldenrod City, save the director of the Radio Station, and he will give you the Silver Wing. Now go to Mahogony Town and go through Ice Path. You are now at Blackthorn City. Clair will be in the Gym to battle after you've completed that mission.
The fifth gym leader in Pokemon platinum is crasher wake but you get the fourth badge.
First you have to battle the snowpoint gym leader
beat the first gym leader in oureburg city he then gives it to you
Maylene is located at Veilstone in Pokemon Platinum. Maylene is a gym leader and is unaware of the amount of strength she possesses.
Pastoria city
volkner
Defeat the 8th
The 8th gym leader in Pokemon Light Platinum is located in a city called Lauren. You can find the gym leader in the Lauren League Headquarters.
The fifth gym leader in Pokemon platinum is crasher wake but you get the fourth badge.
the 8th gym leader is the last
beat the 8th gym and then go up and there is a person from hoen and also gym leader will give it to you
The water Pokemon gym leader is in Pastoria City.
Wallace is the 8th gym leader PEOPLE!!!!!!!!!!!
The Gym Leader of the Snowpoint Gym.
The eighth gym leader in Pokemon platinum is the one in sunny shore city.
After You Defeat All The Gyms Jasmine The 8th Gym Leader Of Johto Should Give It To You.
the 8th gym is closed because you have to beat all other 7 gyms and then it will be open p.s. the 8th gym leader is giovonni