Veneno (Muk) Lv. 65 @ Cleanse Tag
Ability: Sticky Hold / Careful Nature
Moves: Dig, Sludge Bomb, Shadow Punch, Brick Break
Brock
I started off by breeding my Gengar with a freshly caught Muk in Leaf Green, and then trading the newly hatched Grimer with Shadow Punch and Giga Drain to Fire Red. It was a nice surprise seeing that she knew Giga Drain, because I didn't know that TMs are transferred in breeding. I named her Veneno, which means Poison in Portuguese.
Leveling her up was a breeze due to the exp bonus from the trade, but I completely forgot that she could desobey my commands if I didn't have enough badges. Oh well.
The battle against Brock was easy, since Giga Drain OHKOes both of his Pokémon. When Veneno decides to use Giga Drain, that is.
Misty
I tried to avoid all the trainers that I could in Mt. Moon and was doing fine until the last trainer. I had to face the scientist just before the fossils with 3 HP and no potions left. I ended up losing to his last pokémon and had to go through the cave again, but with only one trainer fight at the bright side.
I learned from my mistakes and bought a bunch of Super Potions before facing Misty. It took a few tries, including one that Starmie used Water Pulse, landing a critical hit and confused Veneno, who hurt herself in her confusion, meaning instant loss to one attack, but I managed to defeat her. After obtaining her badge, Veneno began to obey me again until she hit LV 31.
Lt. Surge
I went to Bill, got the S.S. Anne ticket, got the TM for Dig, taught it to Veneno and then borded the ship, battling no one except my rival inside. I taught cut to Cut, my Oddish (pretty creative name, right?), and went to challenge Lt. Surge. Sadly, after his Voltorb I went to lvl. 31, meaning that Veneno won't always obey me anymore (I wonder why Nintendo gives you the exp boost If you can't use the Pokémon properly anyway), but I won the battle with 3 digs and 1 Shadow punch.
Erika
After getting through the Rock Tunnel with no Flash, I went straight to Celadon City. After buying some recovery items, I went to the gym and Veneno evolved to Muk after beating the trainer just before Erika. The battle against her was ok, besides the infinte paralisys. With her badge, I can use Veneno normally until lvl. 50, which is a relief.
I defeated Giovanni in the Rocket Hideout in Celadon and then kicked the Rockets out of the Pokémon Tower.
Sabrina
I forgot to say it, but I teached Brick Break to Veneno the second after she evolved. I went to Silph Co. and defeated Giovanni once again, learning Sludge Bomb in the process.
I then went to Sabrina's gym. The battle wasn't too dificult, since the only Pokémon of hers that actually attacked me was Venomoth using Psybeam, but, despite being super effective, it only hit for 22 damage. I won, and now Veneno will obey me until lvl 70 (Maybe that's enough to beat the last gym).
Koga
When I arrived at Fuchsia City, I went to the Safari Zone and got HMs Surf and Strenght first and then went to battle Koga. The battle wasn't very hard despite not having super effective moves (Well, I used dig against Muk, but all of his other Pokémon have levitate). I won, teached Surf and Strenght to my Lapras, and flew to Pallet Town.
Blaine
I got to Pallet Town, surfed to Cinnabar Island and went to the Pokémon Mansion. After a while, I got the Secret Key and went to the gym. I awnsered all the super hard questions[/sarcasm] and went to battle Blaine. The battle was easy, since I could just use dig until I won.
Giovanni
After flying to Viridian City, I went straight to the gym. Battled every trainer this time, because I was only lv. 60 (I was kinda worried about getting past lv. 70), leveled up a little, and then I went to Giovanni. The battle wasn't very hard, I only had to use 1 Hyper Potion after getting to 19 HP and couldn't use Dig because Earthquake does double the damage if you use it, but I managed to win.
I saved the game.