刚柔相济

gāngróu-xiāngjì

[temper force with grace; the strong and weak mutually assist each other] 刚烈与柔顺相互弥补, 柔硬兼施, 恩威并用

凡为将者, 当以刚柔相济, 不可徒恃其勇。 --罗贯中《三国演义》