After you have defeated the game, when you return to Crag Area's Colosseum, Scraggy and the various other Pokémon will inform you of a Battle Tournament. This Battle Tournament consists of Pokémon, battling it out to see who is the best

Battle Tournament

Details:
To get to the Battle Tournament, you merely have to consult with the Aipom at the entrance to the main area of the Colosseum. This Aipom will invite you to join the tournament

The tournament has several rounds and has you face off against three Pokémon sequentially. You don't get health regeneration so you have to be careful with who you hit. You have the ability of changing Pokémon between the round of the tournament. The Pokémon you battle in this tournament are stronger than when you first faced them so you need to make sure your Pokémon are at a high level.

Backup Pokémon

When you enter the mode, you have the ability to select two Backup Pokémon. Similar to how they'd come in a pinch during normal battles, these Pokémon will come in and attack the enemy, doing damage while they go. This is very useful in order to try and cover any type disadvantages brought on by the other Pokémon you face. To activate them, all you have to do is press the A Button at any time. This calls them into battle and they shall quickly attack, do the damage, and then leave. You can only use each backup Pokémon once per round, and you cannot skip one to get to the other one.

Below are the various rounds of Pokémon you will encounter.

Round One

No. Pic Name Weak Against Resistant To
#92
Scraggy   
#96
Croagunk  Snivy
#85
Ferrothorn TepigPikachu
Snivy
Oshawott

Round Two

No. Pic Name Weak Against Resistant To
#179
Scrafty   
#156
Magmortar OshawottSnivy
Tepig
#155
Garbodor  Snivy

Round Three

No. Pic Name Weak Against Resistant To
#60
Seismitoad SnivyPikachu
Tepig
#83
Excadrill Tepig
Oshawott
Pikachu
#153
Galvantula TepigPikachu
Snivy

Round Four

No. Pic Name Weak Against Resistant To
#112
Throh   
#154
Electivire  Pikachu
#113
Sawk   

Round Five

No. Pic Name Weak Against Resistant To
#138
Escavalier TepigSnivy
#91
Darmanitan OshawottSnivy
Tepig
#7
Krookodile Snivy
Oshawott
Pikachu

Round Six

No. Pic Name Weak Against Resistant To
#170
Charizard Pikachu
Oshawott
Snivy
Tepig
#110
Beartic Tepig 
#118
Rhyperior Snivy
Oshawott
Pikachu
Tepig

Round Seven

No. Pic Name Weak Against Resistant To
#54
Bisharp TepigSnivy
#76
Scolipede Tepig 
#132
Tyranitar Snivy
Oshawott
Tepig

Round Eight

No. Pic Name Weak Against Resistant To
#127
Conkeldurr   
#52
Zoroark   
#133
Salamence  Snivy
Tepig
Oshawott

Round Nine

No. Pic Name Weak Against Resistant To
#103
Druddigon  Pikachu
Snivy
Tepig
Oshawott
 
#102
Garchomp  Pikachu
Tepig
 
#088
Victini Oshawott
 
Snivy
Tepig
 

Round Ten

No. Pic Name Weak Against Resistant To
#129
Golurk Snivy
Oshawott
 
Pikachu
 
#121
Hydreigon  Pikachu
Snivy
Tepig
Oshawott
 
#124
Lucario Tepig
 
Snivy