The phrase "personal fiefdom" refers to a situation where someone has complete control and power over a particular area, organization, or group, as if it were their own personal property. Full definition
«Shelly Silver is the poster - child for professional politicians who create personal fiefdoms for themselves and their corrupt cronies,» he said in the speech. (dnainfo.com)
His vicious personal fiefdom of Candyland becomes a symbol for the sadism, oppression, theft of identity, false assertion of enduring superiority and the corruption of the human spirit that lie behind slavery. (theguardian.com)