is there a weakness to arceas

Its weak against everything, but strong against everything, too, depending on the kind of plate it has.

I mean, Arceus' type depends on the weaknesses of the plate's type it's holding. As a normal Pokemon with no plate, it's only weakness is fight.

ARCEUS WAS NEVER WEAK AND NEVER WILL BE....not that it is invincible though if i was to pick its weakness would be another multi element type pokemon like mew......thats my opinion cause i think another multi type may counter arceus attacks as well.