Harsh
Severe, Cruel, Terrible
independent noun
Something that's cruel tends to be harsh, severe, and terrible. And of course, it's still cruel to boot.
こく
This has the same reading as the kanji you learned, meaning you know the reading!
それをあいつに頼むのは、ちょっと酷すぎやしないか。
Asking that guy for it is a bit too harsh.
あれは、みんな酷な実践方法だったと言っていた。
Everyone was saying it was a severe way to practice.