Malevolent would be just one of many words that could mean extreme cruelty. thesaurus . com would be a great place to start to find other words.
Crudelis means cruel, Atrox means cruel, horror, etc
The word atrocious means very wicked or extremely bad. Some synonyms for atrocious are horrible, cruel, brutal, awful, lousy, rotten, diabolical, and heinous.
vicious person
cruel, brutal, inhuman, ruthless, heartless
hectic
Imperative
Serene means extremely content or peaceful.
A word that means harsh comments is ridicule. To ridicule is to make fun of a person in a mean or cruel way.
"Diabolical" means wicked, evil, or relating to the devil. It is often used to describe something that is extremely cruel or harmful.
One is definition and another one is cruel. or rude
To be diabolical is to be extremely cruel. An example sentence would be: Some people say Hitler's acts were diabolical.
The Spanish word for Cruel is "Cruel" though it is pronounce "Crew-el"