Answer:
Intentionally cruel.
Step-by-step explanation:
In is essay, Sedaris characterized his teacher as a person whose mood depended on good and bad moments instead of good and bad days. He says that his teacher's temperament was unpredictable and she always seemed like a violent person.
According to Sedaris, his teacher was intentionally cruel because he says that she would belittle and use abusive language to anyone she wants to. This can be inferred from the lines "I absorbed as much of her abuse as I could understand" and "The teacher proceeded to belittle everyone".