one-man band
noun [ C usually singular ] uk/ˌwʌn.mæn ˈbænd/ us/ˌwʌn.mæn ˈbænd/
（通常在室外，同时演奏多种乐器的）一人乐队
a musician who performs alone, usually outside, carrying and playing several instruments at the same time
figurative The organization seems to have become a one-man band with just one person making all the decisions. 那个组织似乎变成了个一人乐队，所有的决定都是一个人说了算。