Cruelty, Brutality
noun, な adjective
The remainder of oppression is cruelty. Even when you're done oppressing people the brutality you caused will linger in their minds and hearts.
ざんぎゃく
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
これは非常に残虐な犯行です。
This is an extremely brutal crime.