Walkthrough
With your adventure in the Sevii Islands complete and all the Legendary Pokemon available captured, the only thing left to do in order to complete the Post Game Story is rematch the Elite Four. Since your last time facing them, the Elite Four have gotten even stronger. All of their Pokemon Teams will be at higher levels, and all of them will have replaced at least one of their Pokemon with a 2nd or 3rd Generation Pokemon.
The first member of the Elite Four remains Lorelei, who continues to specialize in using Ice Type Pokemon. Lorelei continues to be weak against Fire Type and Steel Type Attacks, but since three of her five Pokemon are still part Water Types, Electric Type Attacks do great against her as well.
Elite Four Lorelei: Level 64 Dewgong, Level 63 Cloyster, Level 63 Piloswine, Level 66 Jynx, Level 66 Lapras
The second member of the Elite Four remains Bruno, who continues to specialize in using Fighting Type Pokemon. Flying Types still have the upper hand against Bruno's Fighting Type Pokemon, but should you choose to use them against Bruno, watch out for his Steelix because they aren't weak against Flying Types. Psychic Types and Flying Types hit Bruno's Fighting Type Pokemon extremely hard, while Water Types and Fire Types do well against his Steelix.
Elite Four Bruno: Level 65 Steelix, Level 65 Hitmonchan, Level 65 Hitmonlee, Level 66 Steelix, Level 68 Machamp
The third member of the Elite Four remains Agatha, who continues to specialize in using Ghost Type Pokemon. Because four of her five Pokemon are still part Posion Type, Psychic Type Pokemon & Attacks continue to work best against Agatha. However, Psychic Types are weak against Ghost Types, so be aware of the risk/reward.
Elite Four Agatha: Level 66 Gengar, Level 66 Crobat, Level 65 Misdreavus, Level 68 Arbok, Level 70 Gengar
The fourth and final member of the Elite Four remains Lance, who specializes in using Dragon Type Pokemon. Ice Types Attacks still work best against Lance since three of his five Pokemon are extremely weak against them, but Dragon Type Attacks and Electric Type Attacks also work well against his Pokemon Team. Defeat him to face your Rival is the rematch for the ages!
Elite Four Lance: Level 68 Gayrados, Level 66 Dragonite, Level 66 Kingdra, Level 70 Aerodactyl, Level 72 Dragonite
Now that you know about rematching the Elite Four during the Post Game Story, Click Here to learn about rematching your Rival for the Kanto Region Championship during the Post Game Story!