Normally it would be Giratina, but with the special event its Arceus hands down
arceus is i said party not single pokemon.
I'd say mewtwo
the strongest water Pokemon is Palkia
They are not found in the wild in Pokemon Platinum.
well the strongest Pokemon you can catch is raqazza a legendary dragon Pokemon
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?
I think , all of the legendary pokemons.
PIKACHUUUUU
Rayquayza
shymin
Moltas: the fire legendary bird Pokemon the second strongest bird Pokemon
Giratina