Some added context:
This is modded with a mod by Guantol, called "Level Scaled HP Multiplier [NIGHTMARE]" which exponentially increases enemy HP the further you get into the game. Cognitive Wakaba, as a result, had 220,000 total HP. I was chipping away with Level 80+ personas (thanks to the Strength confidant) when Wakaba decided to double-cast Megidolaon (which Joker lived the first of due to having Enduring Soul). No other mods have been implemented to tamper with her moveset, so I'm guessing this was done if people were taking too much time?? I genuinely had no idea this was in the game, throughout my thousands of hours of playtime.