the 8th gym leader is the last
Well,the 3rd gym leader is maylene. She is also gym leader number 3 in diamond and pearl.So no need to worry.
The last gym leader has one
the last gym leader (electric) has the Pokemon octillery
The eighth gym leader in Pokemon platinum is the one in sunny shore city.
you must defeat the last gym leader and capture pickachu
The fifth gym leader in Pokemon platinum is crasher wake but you get the fourth badge.
She is in Hearthrome City, in Platinum she is the 3rd gym leader.
The forth gym leader is in Veilstone City
The Gym Leader of the Snowpoint Gym.
The fourth gym leader is Maylene in Veilstone City, a fighting type gym leader.
Do you mean a gym leader?
You go on to defeat the eight gym leader.