There is no easy way to do it. First up is a dark pokemon trainer so I recommend a fighting or ice pokemon. Next is a Ghost pokemon trainer so try anything but normal and ground(mostly). Then there's an ice pokemon trainer so get a pshychic. And then you face dragon's so get some dragon and ice. And for steven you need fire, ice and ground. Their levels range from 45 to 55 so brings lots of potions, revives and move restorers.

level 100 blazikin

double kick,sky upper cut,overheat,and fire blast

flamer

Sydney(Dark)- Fighting, ice, or fire
Phoebe(Ghost)- Normal, ground, or psychic(PSYCHIC)
Glacia(Ice)- Fire, psychic, or grass
Drake(Dragon)- Kyogre(ICE BEAM ALL THE WAY, BABY)
Steven(Steel)- Fire(Blaziken, Vulpix, Ninetales, or Slugma), (Blaze kick, Flamethrower, Will-o-wisp, or Ember)


WATER TYPES RULE, BUT FIRE TYPES ARE MORE COOL!!!

i noly use 2 pokemons to beat it
it was easy.

Get Kyogre to level 50 and bring many about 10 revives and 10 full restores just in case!
His skills should be:
Calm Mind (Use it 6 times on the 1st pokemon any of the elite will call)
Ice beam
Surf or Hydro Pump(Mine's surf because of it's high accuracy)
Thunderbold or Thunder(Mine's Thunderbolt because of it's high accuracy)

rape the people so they say your discusting and they leave so molest and hump their
pokemon and make tiny pika*****s. HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA!