"OP" achivement not popping

[Semirhage]

So I was grinding on floor 3, got Sif to level 99 and then kept killing regular sadness to get everyone else to 75 (Did not loop between getting Sif to max and then everyone else).
Achievement didn't pop so I continued to the end and that still didn't work.
Any tips on if I have done something wrong for the achievement or how to get it to pop?

[AriesIgnitor]

Did you grind on a "fresh" run? I believe it will only trigger the achievement once you've grinded everyone to level 75 from their base levels (I.E: from when you all enter the house) in a single loop. Don't worry about Siffrin at this point, it'll still count even if he's already level 99.

[Semirhage]

Just tried this and it still didn't pop :(

[medea]

Sometimes you need to fight and beat a new sadness after you already got everyone to max for the game to realize you hit the criteria for the achievement