出典:Wiktionary
From Shakespeare's Hamlet, Act 3, Scene 4: "I must be cruel, only to be kind: / Thus bad begins and worse remains behind."
be cruel to be kind (三人称単数 現在形 is cruel to be kind, 現在分詞 being cruel to be kind, 過去形 was cruel to be kind, 過去分詞 been cruel to be kind)