https://www.serebii.net/ultrasunultramoon/battleagency2.jpg
https://nintendosoup.com/wp-content/uploads/2017/11/BattleAgency_350x350-150x150.png
To get to Grade 50 (Level 100 rental Pokemon) in the Battle Agency, you need to win 450 battles.
Grades 0-10: Level-up every 3 battles. (3 battles = 1 grade level-up.) Win 30 battles to reach Grade 10, totaling 30 overall.
Grades 10-20: Level-up every 6 battles. (6 battles = 1 grade level-up.) Win 60 more battles to reach Grade 20, totaling 90 overall.
Grades 20-30: Level-up every 9 battles. (9 battles = 1 grade level-up.) Win 90 more battles to reach Grade 30, totaling 180 overall. After level 30, things start to become really tedious, as leveling up one rank takes much longer.
Grades 30-40: Level-up every 12 battles. (12 battles = 1 grade level-up.) Win 120 more battles to reach Grade 40, totaling 300 overall.
Grades 40-50: Level-up every 15 battles. (15 battles = 1 grade level-up.) Win 150 more battles to reach the highest rank, Grade 50, totaling 450 overall.
So it would take 450 victories to reach the highest rank, Grade 50 (level 100 Pokemon.) However, really you can stop at Grade 30 (180 battles.) Nothing beyond that is worth any rewards you might get.
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