"Barbarousnesses" is not a commonly used word, and it might be difficult to find synonyms for it. However, some possible alternatives could be "cruelty," "savagery," "brutality," "inhumanity," "atrociousness," or "barbarism." These words describe a state of being barbarous or lacking in compassion or civilized behavior. They can be used to refer to violent or ruthless acts committed by individuals or groups, such as war crimes, acts of terrorism, or other forms of violence. While the term "barbarousnesses" might not be in common usage, there are still plenty of other words that carry similar meanings and convey the same sense of violence and brutality.