Well first you need to free the fairy Pokemon trio. Then go to mount coronet.
After that you have to fight some galantic people then catch or defeat diagle. Then go to sunnyshore city. First you see flint at gym then go and get the gym leader
Volner from the lighthouse. Hope that helps.
The 8th Badge in Pokemon Diamond is called The Beacon Badge.
Sunyshore city, where the last gym badge will be.
you can cheat and only get the last badge but apart from that you can only use waterfall as a move in a battle . you have to have the last badge
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In Diamond, Badge 5 can be gotten by defeating Fantina in her Gym in Hearthome City.
the 7th gym leader is in sunyshore city and he is the user of electric type pokemon all you gotta do is beat him and all the trainers and he will give you the badge just like the others
Hearthome
The lose of dignaty you had
hearthome city
Hearthome City.
the seventh gym badge snowpoint gym
GET THE LAST BADGE......