ok i havent beaten it but you need all pokemon around level 70 (ish) or higher (i think). mine are all at 100. you need at least 2 ghost pokemon and 1 poison pokemon and the rest dont matter. but the ghost and poison pokemon will not be affected by the muk. the other 3 must be pulled out when muk gets near them so be careful.
with pokemon
go to the next gym leader.
Soul Badge (Fuchsia Gym)
use 3 seakings with aqua ring or water fall and you are done
The fifth Gym can be found in Fuchsia City. The leader is Koga, who specialises with Poison-type Pokémon.
with pokemon
The gym leader is in the fuchsia city gym. Its not koga its his daughter janine because koga is part of the elite four now.
Ypu Find her at the gym at the south most part of the city in Fuchsia city.
The gym leader of Fuchsia City is in her gym. It is located in the same strip as the Pokemon Center. They all look the same because they are ninjas, so it is a guess and choose game in the gym.
Fuchsia city.
go to the next gym leader.
The Gym and Gym leader is in the bottom left of the city near the Pokemon center.
kill it
He is the fuchsia city gym leader.
She is in Fuchsia City
it is in FUCHSIA CITY or CINNABAR ISLAND
Its on cinnabar island, you will need to use surf to get there from fuchsia city ^.^