[adverb]From 1960 to 1970, Ayatollah Mohsen al-Hakim reigned supreme among the Shi'ites of Iraq, Lebanon, Iran, Pakistan and elsewhere.(figurative) In the nurseries of Britain, the teddy bear still reigns supreme (= has the most importance).
SUPREME
Meaning of SUPREME in English
Cambridge English vocab. Кембриджский английский словарь. 2012