Your first duel is with Lorelei, Mistress of Icy Pokémon. Fire-type, Fighting-type, and Rock-type Pokémon all have a combat advantage against Ice-types. Many of her Pokémon also have Water-type characteristics, so be sure to guard against those powers too.
Bruno
Pokémon
Level
Onix
53
Hitmonchan
55
Hitmonlee
55
Onix
56
Machamp
58
Bruno is the second of the Elite Four trainers. Fighting-type Pokémon are his specialty, but he also has two Onix to round out his squad. If you want to go the distance, remember that Flying-type and Psychic-type Pokémon are more than a match for Fighting-types.
Agatha
Pokémon
Level
Gengar
56
Golbat
56
Haunter
55
Arbok
58
Gengar
60
If it's a challenge you want, then Agatha is ready to deliver. As you may or may not know, no type of Pokémon has a great advantage in battle over Ghost-types, and some special attacks won't affect them at all. Focus on Water- or Fire-type attacks.
Lance
Pokémon
Level
Gyarados
58
Dragonair
56
Dragonair
56
Aerodactyl
60
Dragonite
62
Lance is the leader of the Elite Four and the most powerful trainer in the Pokémon League. His Dragon-type Pokémon are vulnerable to Ice-type and Fighting-type powers. On the other hand, no Pokémon can defend well against Dragon-type attacks, so keep lots of Potion ready.
Gary
Pidgeot
61
Alakazam
59
Rhydon
61
Gyarados
61
Exeggutor
61
Arcanine
61
Arcanine
63
Gyarados
63
Exeggutor
63
Venusaur
65
Charizard
65
Blastoise
65
(Chose
Bulbasaur)
(Chose
Charmander)
(Chose
Squirtle)
Gary defeated the Elite Four before you even set foot on Victory Road, and now you must beat him if you want to claim the title of World's Greatest Pokémon Trainer. The first half of his team consist of Pidgeot, Alakazam, and Rhydon. The second half differs from game to game, depending on which Pokémon he chos when the game began. If your Pokémon are level 74 or above, you should be able to defear Gary's Pokémon with just a couple attacks each, but you should still be ready to defend against his Pokémon's special attacks.