As someone who did 96 consecutive Battle Royals with level 1 pokemon to auto lose so I could get all the power items immedeatly, i'd have to say that this mode is by no means balanced or fair, but certain kinds of pokemon and setups can overtake it easily.
Pokemon with resist synergy, priority moves, and sweeper stats excel in royal. Build a team for it, and you'll overtake it OP, good luck.
Also shiny pokemon and mega forms you cant use appear in it as well, was pretty mad.
