People said that they could defeat each member of the elite four in all known regions, however,they have been defeated by 2 trainers whose objectives were never to be champions.
It is even rumored that one of those trainers defeat them with the help of a single pokemon possessor of a mega evolution, but it identity is unknown and they refuse to mention the pokemon winner
The members are:
Glacia Collins (ice type pokemon trainer)
Nathan Hughs (ground type pokemon trainer)
Anna Burns (fire type pokemon trianer)
Tyson Murray (steel type pokemon trainer)