What type of government is characterized by a single leader or small group holding power?

A government characterized by a single leader or a small group holding power is most accurately described as totalitarian. In a totalitarian regime, the governing body not only controls the political landscape but often penetrates many aspects of public and private life. This system centralizes authority under a dominant leader or party, allowing little to no opposition or dissent, effectively eliminating democratic processes.

While oligarchy might seem similar because it refers to a small group having control, it does not necessarily include the same level of repression or control over all aspects of life that characterizes totalitarianism. Democracy and republic specifically denote systems that typically allow for more public participation and representation, which are not features of totalitarian regimes.