depends
Get the best pokeballs and go search for it.
well of course arceus but u can only get it on a wifi event
Giratina, Because it is on the front of the box.
the rarest Pokemon in ANY game is Arceus. also i would say evee and ditto, gible but mainly arceus
there are lots ! there is bulbsaur weepingbell and lots the most rarest is poison type
The rarest Pokemon is Dialga
there is no rarest Pokemon you have to train and train and including shinies there is no real rarest Pokemon at all.
arceus
You could only get Arceus through the event system, which means outside of cheating there is no way to get it currently.
its the rarest thing in the underground also it behind the Pokemon statue in Eterna City
mew2 is the rarest
well it depends i would personally think gabite in victory road it took me at least 45 wild encounes to find one