diagla charizard lucario palkia mew and monferno
A lv:100 venusuar!!
There is no best Pokemon.All Pokemon are weak and strong against others.
Have a good Fire and/or Ground Type...
weedle, sparrow, geodude, nosapass, skitty
victory road
Venusaur,Rapidash,Gyarados,Pikachu,Pidgeot and Dragonite
You need a grass type, a fire type, a water type, an ice type, your legendary and a ghost or dark pokemon.
Fire and water are the best combination to beat the elite 4.
NOT ACTION REPLAY!!! I say elite 4 and if you're leveling up weak pkmn, give'em an exp.share and put your strongest Pokemon in slot 1 of your party.
Lugia because it is physic and super affective against poison and fighting but don't use it against dark because they will kill it easily
Diamond is not a Pokemon but i think Arceus is one of the strongest Pokemon ever.
The best thing to do is to continue to go through the elite 4 and give that Pokemon the exp. share.