Arceus
in the national pokedex: arceas in the regular pokedex: dialga
if you meen the national dex then you need to find every Pokemon in the sinnoh pokedex
Garatina...
THE LAST FIVE POKEMON IN THE POKEDEX IN DIAMOND IS UXIE MESPRIT AZELF DIALGA AND PALKIA. NOTE: PALKIA CANT BE CAUGHT UNLESS YOU TRADE WITH SOMEONE.
Arceus
Palkia, the one on the cover of Pearl.
The last Pokemon in the National Pokedex is number 493, Arceus.
Mew is the last generation 1 Pokemon in the National Pokedex.
He is in Sandgem Town, in the Pokemon Lab after you see all the Sinnoh Region Pokemon. He will present you with the National Pokedex. After your pokedex is complete (note: you do not need to own all the pokemon) visit Professor Rowan. Professor Oak will come and give you the National Pokedex. After, he's in Pal Park, which is at the end of route 211. You'll see him there, then he'll leave. After that, he's in the last house to the left in Eterna City.
Send me to hell if I´m wrong, but I believe you have to get the national pokedex. How to get the national pokedex? SEE all the pokemons!
yes arcaeus is the last Pokemon in the pokedex
To catch every Pokemon, you need action replay for the few last diamond legendaries. You will need Pokemon fire red/leaf green and emerald. Migrate them to Pokemon diamond. In Pokemon diamond, fill up your pokedex by catching Pokemon normally or with poke radar, or use gts. It will take a long time to catch all Pokemon