Technically, there isn't any that is better than the other. All Pokemon Types are the same, no matter the weakness.
arceusKyogre is the strongest water type Pokémon.
There are many Water Type Pokemon in Pokemon Platinum, however, there is only one strongest one. That Pokemon is Palkia. Palkia is one of the Main Storyline Legendaries in Pokemon Pearl, it is a Water/Dragon Type. If you are looking for the strongest Non-Legendary, your best bet is Gyarados. Any exceptions?
The strongest electric type would be Zapdos.
Darkrai?
Rayquaza.
Technically Cyndiquil is the strongest but it all depends on what type of Pokemon you want.
no strongest. just depends on who has the type advantage in a battle. they're all great pokemon!
Fire type has the very strongest advantage over Grass type Pokemon
Rayquaza the Legendary Sky Dragon is the Cover Pokemon of the game Pokemon Emerald... But that does'nt mean it's the strongest... It still depends on the type of Pokemon... Do you know that a good built Ice Type Pokemon can 1-hit-defeat a Dragon Type Pokemon like Rayquaza?
grass knot
Probally Mew or Mewtwo
my opinion is lugia.