na-adjective, noun
cruel; heartless; brutal; atrocious
A yojijukugo describing a person or act as extremely cruel and merciless. Often used in literary or emphatic contexts.
彼の残忍酷薄な仕打ちに、誰もが言葉を失った。
Everyone was speechless at his cruel and heartless treatment.
その歴史書には、残忍酷薄な拷問の記録が残っている。
That history book contains records of brutal and atrocious torture.
A yojijukugo combining 残忍 (cruel) and 酷薄 (heartless, atrocious). The exact historical derivation is uncertain, but it is a literary compound used to intensify the sense of cruelty.