How Can I Beat The Elite Four In Pokemon Diamond?

I have a way AND it's rather EASY! First I would have to take AWAY Dialga, Empoleon is your Steel Type and, to be honest, Dialga isn't the best dragon to use in the Elite Four. So I suggest you add to your team:

Roselia/Roserade:

Poison Jab
Petal Dance
Magical Leaf
Gigadrain

Rapidash:

Solarbeam
Flamethrower
Fire Blast
Bounce

Garchomp:

Crunch
Dig
Brick Break
Dragon Claw

Gyarados:

Ice Fang
Fire Blast
Dragon Pulse
Aqua Tail

Luxray:

Crunch
Spark
Thunderbolt
Iron Tail
So, I painstakingly constructed this team and movesets to battle the Elite Four. So here is the way to use it:

Strategy for Aaron:

1. Use Empoleon’s Drill Peck/rapidash on  
    Dustox.
2. Use Gyarados’s Fire Blast or Luxray on Beautifly.
3. Use Rapidash for Heracross.
4. Use Gyarados’s Fire Blast on Vepspiquen.
5. Use Empoleon’s Earthquake on Drapion.

Strategy for Bertha:

1. Use Roserade on Quagsire.
2. Use Roserade on Sudowoodo.
3. Use Gyarados to wither Whiscash.
4. Use Gyarados’s Aqua Tail or Roserade on Golem.
5. Use Gyarados’s Aqua Tail or Roserade on Hippowdon.

Strategy for Flint:

1. Use Empoleon’s Surf on Rapidash.
2. Use Crunch or Luxray on Drifblim.
3. Use Empoleon’s Surf on Steelix.
4. Use Physical moves on Lopunny.
5. Use Garchomp on Infernape.

Strategy for Lucian:

1. Use Crunch on all her Pokemon but Bronzong.
2. Use Gyarados’s Fire Blast on Bronzong.

Strategy for Cynthia:

1. Use Garchomp on Spiritomb.
2. Use Gyarados’s Fire Blast on Lucario.
3. Use Roserade on Gastrodon.
4. Use Luxray’s Spark on Milotic.
5. Use Rapidash/Empoleon’s Ice Beam on Roserade.
6. Use Gyarados’s Ice Fang/Dragon Pulse/Empoleon's Ice Beam on Garchomp.

I used pokemon that would either 1HKO/2HKO the Pokemon or not be weak against that Pokemon. I also assigned moves to cover the Elite Four, so kick some butt!

You have to get all your pokemon to level 100 that worked for me my team infernape luxray giratina floatzel garchomp dialga hope it helps

Always have super effective attacks for bug pokemon, ghost pokemon, fire pokemon and ground pokemon. Also carry hyper potions, elixer, and full restores. Also you must have at least 4 or 5 strong pokemon and not just 2.

Good luck and I hope this helps!!! ;)

You will need a level 72 dialga level 70 palkia level 73 garchomp level 73 infernape level 71
staraptor and a rapidash level 71-72. A good pokemon leage team level should be 65/75.this is
the way I'm doin' it ,so you don't have to follow my rules.

You need to get Empoleon and Dialga to level 60 and train a grass type to level 55+, fire type to level 52+, Ghost type to level 55+, and any pokemon with good defense/hp to level 40+.

My team: Infernape level 57
Roserade level 55
Floatzel level 55
Dialga level 59
Gengar level 58
Snorlax level 46

Items: 30 hyper potions
20 revives
15 full heals
15 full restores
10 max potions

Items left over: 11 hyper potions
8 revives
10 full heals
3 full restores
9 max potions

I beat the Elite Four the first time around with the following pokemon:
Lv. 51 Dialga
lv. 50 Machamp
lv. 50 Staraptor
lv. 53 Torterra
lv. 51 Empoleon
lv. 50 Raichu
Make sure you know which types are super effective against theirs so you can take them out quickly. Also be sure to heal after each battle, and don't be skimpy on revives, super/hyper potions ect.

Get pokemon up to at least level 60 to win

Get all your Pokemon to level 100

First of all you need to level up your pokemon to level lets say 60-65 then you have a gud chance of takeing em on  trust me I tried takin em on wif pokemon lvl 40 to 50 and they still wuped me hope this helps gud luck

You should have most of the Pokemon in your party at Level 60 to have a good chance to beat the elite four. Just two Pokemon won't do it.

You have to have a lot of very good pokemon like Dialga and palkia and Giratina and Frosslass and Purugly and skunk tank and all on LV.100

For the first elite use fire or flying type. . Second elite water,grass and ice type. . Third elite water and ground type. .  Fourth elite dark or ghost type. . Cynthia(champion). . It is a mix. .

I used a level 81:empoleon,level 79 palkia or diagle,level 75:starraptor or garchomp that knows arial ace and thats how I beat the elite four hope this helps

You can go to pokedram.com and go to games then click on the game you hae and there will be a walkthrough

Number1  never choose piplup as starter my advice get chimchar off gts