@Lucrecia
But against wizards or warriors prepared for their Modus operandi they're probably not that dangerous.
I definitely don't think that's correct, or at least, certain demons are exceptional just as certain humans are exceptional. The hero party we saw was only one of them and it was lauded for its successes precisely because the threat was very real. Qual remember was so dangerous that they couldn't actually defeat him at all but merely managed to seal him. 80 years was enough of a freeze and human development fast enough that new generations could counter him, but even so he managed to almost instantly analyze the multi-year-development extremely complex defense magic created to counter Soul Track. He was definitely not a being to allow to get away, Frieren correctly finished him right off but if he escaped and had a few years to do his own R&D there is no telling whether he might have developed a counter-counter himself.
I agree that the average demon is stronger then the average human but humans gain strength in numbers and better humans can still win particularly with real teamwork, but at the top end both humans/dwarves/elves and demons are all extremely dangerous. This will be an interesting fight in part because Aura has presumably not been sealed like Qual was, and even if she wasn't quite as dangerous or a battle maniac she's also had decades now. Frieren and humanity have grown, and both Fern and Stark are very impressive in their own right, but Aura has probably had a long period to consider the demon king's defeat so we'll get a chance to see if demons can grow as well.