Yoma are killed by beheading. A human trained in swordsmanship can do it, but yoma are also capable of disguising themselves as human, and humans can't detect them unless they reveal themselves, or unless one of my kind is there to detect them. And if one of my kind is there, it's generally easier to let us kill them.

Awakened Beings are much harder to kill, and often have to be cut to pieces because many of them are capable of regenerating themselves and beheading them isn't always enough. My kind are typically sent out in groups of four to fight them - only the very strongest of us are capable of taking them down alone.

[Cassandra had been one of those very strongest warriors, though; she'd always fought Awakened Beings alone, and won.]

Abyssal Ones... are typically avoided. You need a lot of my kind to do it, or to hope that they kill each other.