To get the final badge in Pokemon yellow, simply have all 7 other badges, (You also must have beaten Giovanni at both the Game Corner and Silph Co.) and go back to Viridian City, the Gym will now be open. Find your way through the maze and go to the Gym Leader, It's Giovanni from Team Rocket! His Pokemon are Dugtrio, Persian, Nidoqueen, Nidoking, and Rhydon. Good luck!
At the gym in viridian city.
just complete the pewter gym (chapter 1)
It's erika the grass type user. the badge is the rainbow badge
GET THE LAST BADGE......
Beat team rocket at Mt moon, Pokemon tower, rocket game corner and silph co. Then get the 7th badge now you can go into the viridian city gym to get the last badge.
The sixth badgeno actually it the third badge
viridian city
Erica in Celadon City.
Go to celadon city.
after you get the thunder badge talk to officer jenny
Get the Thunder Badge And Talk To Jenny And She Will Give You One
Strength will activate when you get the RainbowBadge.
When you get the second badge from Misty, Pokemon you receive in trades up to level 30 will listen to you., while Pokemon with the same ID as your Yellow Version will always listen. When you get the fourth badge from Erika, Pokemon you receive in trades up to level 50 will listen to you, while Pokemon with the same ID as your Yellow Version will always listen. When you get the sixth badge from Sabrina, Pokemon you receive in trades up to level 70 will listen to you, while Pokemon with the same ID as your Yellow Version will always listen. When you get the eight badge from Giovanni, ALL Pokemon will listen to you, no matter what level or what their ID is.
The last gym badge is in viridian city for Kanto. For Johto it is in Blackthorn city.