Like the term "tyrant" (which was originally a respectable Ancient Greek title), and to a lesser degree "autocrat", "dictator" came to be used almost exclusively as a non-titular term for oppressive, even abusive rule, yet it had rare modern titular use.
In modern usage, the term "dictator" is generally used to describe a leader who holds and/or abuses an extraordinary amount of personal power. Dictatorships are often characterised by some of the following traits: suspension of elections and civil liberties; proclamation of a state of emergency; rule by decree; repression of political opponents without abiding by the rule of law procedures; these include one-party state, and cult of personality.
The term "dictator" is comparable to – but not synonymous with – the ancient concept of a tyrant; initially "tyrant", like "dictator", did not carry negative connotations. A wide variety of leaders coming to power in a number of different kinds of regimes, such as military juntas, one-party states and civilian governments under a personal rule, have been described as dictators. They may hold left or right-wing views, or they may be apolitical.
Originally an emergency legal appointment in the Roman Republic, the term "Dictator" did not have the negative meaning it has now. A Dictator was a magistrate given sole power for a limited duration. At the end of the term, the Dictator's power was returned to normal Consular rule whereupon a dictator provided accountability, though not all dictators accepted a return to power sharing.
The term started to get its modern negative meaning with Cornelius Sulla's ascension to the dictatorship following Sulla's second civil war, making himself the first Dictator in more than a century (during which the office was ostensibly abolished) as well as de facto eliminating the time limit and need of senatorial acclamation. He avoided a major constitutional crisis by resigning the office after about one year, dying a few years later. Julius Caesar followed Sulla's example in 49 BC and in February 44 BC was proclaimed Dictator perpetuo, "Dictator in perpetuity", officially doing away with any limitations on his power, which he kept until his assassination the following month.