Cynthia

General Info - Undoubtably the strongest of the Elite Four, Cynthia uses many different types making it impossible to take her entire team down with one type, asuming you don't have any super high level Pokemon on your team. You will be switching a lot in this battle, and you will probably have to use one or two Revives. A full team of six Pokemon doesn't make this battle any easier either.

Lv61 (Ghost/Dark) - Spiritomb has high defences and no weaknesses, which could make it difficult to take down quickly. It will also use the move Embargo, preventing you from using any items for five turns. This can really hurt you if you're up against Spirtomb in the late battle, preventing you from healing.

Lv60 (Grass/Poison) - Fire, Ice, Psychic are your best choices for taking down Roserade, who has high special attack. Don't get caught on the wrong end of Energy Ball or Shadow Ball and you should be fine.

Lv60 (Water/Ground) - Take Gastrodon out just like you did with Bertha's Quagsire and Wishcash. Water/Ground has a 4x weakness to Grass and as I've said before will fall to any good Grass type. If you don't have a Grass type attack however, Gastrodon can be difficult with it's high defences.

Lv63 (Steel/Fighting) - First of all, Lucario does not resemble a Steel type in any way, yet it is, and therefor is weak to Fire, Ground, and Fighting. Steel neutralizes Fighting's weaknesses so Psychic and Flying won't work. Lucario has high special attack but non-impressive defence, so survive it's attacks and then KO it.

Lv63 (Water) - Milotic goes under the classification of "Bulky Water" and lives up to the name. Water is weak to Grass and Electric and Milotic will NOT go down easily without those types. Milotic also has some pretty decent attacking power too so watch out. Remember to be careful while using Grass types as Milotic has Ice Beam

Lv66 (Dragon/Ground) - The pièce de résistance of Cynthia's team is definetly Garchomp with high speed and attack and could very well end your Elite Four challenge. It has Earthquake and Dragon Rush, and both are very powerful moves although the latter does not have the best accuracy. It also has Hyper Beam, which in reality is one of the worst moves in the game. Hyper Beam is now a special attack in DP, so use a Pokemon that can withstand it (most should be able to stay in after one blast) and destroy Garchomp with an Ice attack or heal one of your Pokemon on your free turn.