帝国(dì guó) - empire in Mandarin

帝国 (dì guó) is an empire, a state under an emperor. It is the standard word in history writing and in the news: 罗马帝国 the Roman Empire, 大英帝国 the British Empire, 帝国主义 imperialism.

The figurative use travels exactly as it does in English. 商业帝国 is a business empire, 媒体帝国 a media empire, and the tone is the same slightly wary admiration at something that has grown too big to argue with.

The trap is confusing 帝国 with 王国. 王国 is a kingdom, headed by a 国王; 帝国 is headed by a 皇帝 and implies conquered territory beyond the home country. Britain has both words attached to it in Chinese for exactly that reason, and picking the wrong one changes the size of what you are describing.