What is the meaning of of the phrase
hideous cruelty

The phrase could be translated as being extremely mean or rude, such as in the play much ado about nothing by Shakespeare Beatrice and benidict are at a masked ball and benidict is pretending to be someone else and was talking to Beatrice when she started insulting benidict, he got offended and was down hearted. Another example is hitler and how he treated the Jews.

Can't really answer this question without any background context or the passage.