@Leo80221 It's presently hard to get a read on just what Balam is capable of considering his default demeanor, but we do know he's one of the most powerful demons among the faculty. Kalego mentioned Balam's the only other Chet ranked demon aside from himself among the staff; there's only two ranks higher that according to the scale we were given in the early chapters.
@Leo80221 I mean there's some in-rank pecking order there either way. Either Opera is an 8 and picks on Kallego despite being the same rank, or Opera is a 9 that serves another 9 despite being of the same rank.
@pburgund judging from what we've been told, it seems like being a 10 basically means you have to be the demon lord, and none of the main 3 people WANT to be the demon lord, so it wouldnt surprise me if they were all intentionally avoiding ranking up, meaning they are effectively 10s
@pburgund From what I inferred from the conversation between the top three in the anime is that Sullivan is actually Rank 10 and the strongest of the three, but he refuses to take the ranking test to make it official.