“"When I was that age, I listened to my elders," Onua muttered, conveniently forgetting she had done no such thing.”
A BBEG battle is difficult to get right. You want players to be challenged to their very limits, whilst also avoiding a TPK (though the closer it is, the better). If you nearly kill everyone before the BBEG falls, then you’ve got it just right. If you actually kill everyone before the BBEG falls, then you’ve just had a big waste of time.
Designing your BBEG is challenging enough. Giving it the staying power to last through the encounter, without upping the damage to make a TPK, is partly based on planning and partly about making judgement calls and lying about your rolls.
“Wonder Woman is there to kick ass not give you a boner”