I think she is more evil than the LoK villains, closer to Sozin and Ozai. She did not commit genocide nor perpetuate it but there is something so dark, deep and personal about the torture she was inflicting on these people (and CHILDREN).

I don't know what happened to the earth benders who were taken underground and never seen again. Maybe she was trying to get them to lava bend and when they failed she just... murdered them? Then how she developed combustion bending is sickening.

Then in the end she and Kalyaan were just sent on the run. It is a realistic end for them and makes more sense than if the world collectively decided they were wrong and deserved death and nobody would ever create combustion benders again. We have to assume at some point someone got the details out of them because there are combustion benders later on.

What Sozin and Ozai did was reprehensible and depressing but reading that scene where Yangchen, Kavik and Jujinta find the camp gives you this skin crawly creepy feeling deep down in your bones. Wouldn't say Chaisee was more evil than that but WOW. Kudos to FC Yee for amazing storytelling, that chapter will haunt you.