In my opinion, Absol and Duskull are the best.
This is zeusfireair:
Absol is pretty good for a dark type, but you get it late in the game. If you want to get a good dark type early on, catch a poochyena and evolve it into mightyena. Also if you are lucky enough to get a seedot, try to evolve it into a shiftry with a leaf stone, as its a grass dark type.
swampert or blaziken are the best type to beat gyms or Pokemon league
Darkrai.
ghost or dark types
Dark-type pokemon are resistant to Dark and Ghost moves, and are unaffected by Psychic.
no...
That's a weird question. I think you mean "Are there Dark type Pokemon in Pokemon Ruby?" The answer is "yes." Im pretty sure he was asking what dark Pokemon are in ruby
Sydney (dark type pokemon), Phoebe (ghost type pokemon),Glacia (ice type pokemon), Drake (dragon type pokemon), and Steven is the Champion (steel type pokemon).
pelipper
swampert or blaziken are the best type to beat gyms or Pokemon league
Darkrai.
Use strong water or dark type Pokemon
Type Pokemon Ruby and then type CCG.
Gyarados is probably the best, it is evolved magicarp.
Ghost or dark pokemon
the first elite four in Pokemon ruby is Sidney (DARK TYPE) He has a Mightyena, Cacture, and Crawdaunt note:he will have two Mightyena's
any Pokemon that is a dark type any Pokemon that is a dark type
ghost type Pokemon are immune to normal and fighting type moves and psychic, dark, and ghost types are 2x effective against them.